!0 = metadata !{metadata !"branch_weights", i32 1, i32 7}
!1 = metadata !{metadata !"branch_weights", i32 3, i32 4}
-; The current BlockFrequencyInfo algorithm doesn't handle multiple entrances
-; into a loop very well. The frequencies assigned to blocks in the loop are
-; predictable (and not absurd), but also not correct and therefore not worth
-; testing.
+; Irreducible control flow
+; ========================
;
-; There are two testcases below.
+; LoopInfo defines a loop as a non-trivial SCC dominated by a single block,
+; called the header. A given loop, L, can have sub-loops, which are loops
+; within the subgraph of L that excludes the header.
;
-; For each testcase, I use a CHECK-NEXT/NOT combo like an XFAIL with the
-; granularity of a single check. If/when this behaviour is fixed, we'll know
-; about it, and the test should be updated.
+; In addition to loops, -block-freq has limited support for irreducible SCCs,
+; which are SCCs with multiple entry blocks. Irreducible SCCs are discovered
+; on they fly, and modelled as loops with multiple headers.
+;
+; The headers of irreducible sub-SCCs consist of its entry blocks and all nodes
+; that are targets of a backedge within it (excluding backedges within true
+; sub-loops).
+;
+; -block-freq is currently designed to act like a block is inserted that
+; intercepts all the edges to the headers. All backedges and entries point to
+; this block. Its successors are the headers, which split the frequency
+; evenly.
+;
+; There are a number of testcases below. Only the first two have detailed
+; explanations.
;
; Testcase #1
; ===========
; loop as a whole is 1/4, so the loop scale should be 4. Summing c1 and c2
; gives 28/7, or 4.0, which is nice confirmation of the math above.
;
-; However, assuming c1 precedes c2 in reverse post-order, the current algorithm
-; returns 3/4 and 13/16, respectively. LoopInfo ignores edges between loops
-; (and doesn't see any loops here at all), and -block-freq ignores the
-; irreducible edge from c2 to c1.
-;
+; -block-freq currently treats the two nodes as equals.
+define void @multientry(i1 %x) {
; CHECK-LABEL: Printing analysis {{.*}} for function 'multientry':
; CHECK-NEXT: block-frequency-info: multientry
-define void @multientry(i1 %x) {
-; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
entry:
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
br i1 %x, label %c1, label %c2, !prof !2
-; This is like a single-line XFAIL (see above).
-; CHECK-NEXT: c1:
-; CHECK-NOT: float = 2.142857{{[0-9]*}},
c1:
+; CHECK-NEXT: c1: float = 2.0,
+; The "correct" answer is: float = 2.142857{{[0-9]*}},
br i1 %x, label %c2, label %exit, !prof !2
-; This is like a single-line XFAIL (see above).
-; CHECK-NEXT: c2:
-; CHECK-NOT: float = 1.857142{{[0-9]*}},
c2:
+; CHECK-NEXT: c2: float = 2.0,
+; The "correct" answer is: float = 1.857142{{[0-9]*}},
br i1 %x, label %c1, label %exit, !prof !2
-; We still shouldn't lose any frequency.
-; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
ret void
}
+!2 = metadata !{metadata !"branch_weights", i32 3, i32 1}
+
; Testcase #2
; ===========
;
; step, c1 and c2 each get 1/3 of what's left in c1 and c2 combined. This
; infinite series sums to 1.
;
-; However, assuming c1 precedes c2 in reverse post-order, the current algorithm
-; returns 1/2 and 3/4, respectively. LoopInfo ignores edges between loops (and
-; treats c1 and c2 as self-loops only), and -block-freq ignores the irreducible
-; edge from c2 to c1.
-;
-; Below I use a CHECK-NEXT/NOT combo like an XFAIL with the granularity of a
-; single check. If/when this behaviour is fixed, we'll know about it, and the
-; test should be updated.
-;
+; Since the currently algorithm *always* assumes entry blocks are equal,
+; -block-freq gets the right answers here.
+define void @crossloops(i2 %x) {
; CHECK-LABEL: Printing analysis {{.*}} for function 'crossloops':
; CHECK-NEXT: block-frequency-info: crossloops
-define void @crossloops(i2 %x) {
-; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
entry:
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
switch i2 %x, label %exit [ i2 1, label %c1
i2 2, label %c2 ], !prof !3
-; This is like a single-line XFAIL (see above).
-; CHECK-NEXT: c1:
-; CHECK-NOT: float = 1.0,
c1:
+; CHECK-NEXT: c1: float = 1.0,
switch i2 %x, label %exit [ i2 1, label %c1
i2 2, label %c2 ], !prof !3
-; This is like a single-line XFAIL (see above).
-; CHECK-NEXT: c2:
-; CHECK-NOT: float = 1.0,
c2:
+; CHECK-NEXT: c2: float = 1.0,
switch i2 %x, label %exit [ i2 1, label %c1
i2 2, label %c2 ], !prof !3
-; We still shouldn't lose any frequency.
-; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
ret void
}
-!2 = metadata !{metadata !"branch_weights", i32 3, i32 1}
!3 = metadata !{metadata !"branch_weights", i32 2, i32 2, i32 2}
-; A reducible loop with irreducible control flow inside should still have
-; correct exit frequency.
-;
+; A true loop with irreducible control flow inside.
+define void @loop_around_irreducible(i1 %x) {
; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_irreducible':
; CHECK-NEXT: block-frequency-info: loop_around_irreducible
-define void @loop_around_irreducible(i1 %x) {
+entry:
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
+ br label %loop
+
+loop:
+; CHECK-NEXT: loop: float = 4.0, int = [[HEAD:[0-9]+]]
+ br i1 %x, label %left, label %right, !prof !4
+
+left:
+; CHECK-NEXT: left: float = 8.0,
+ br i1 %x, label %right, label %loop.end, !prof !5
+
+right:
+; CHECK-NEXT: right: float = 8.0,
+ br i1 %x, label %left, label %loop.end, !prof !5
+
+loop.end:
+; CHECK-NEXT: loop.end: float = 4.0, int = [[HEAD]]
+ br i1 %x, label %loop, label %exit, !prof !5
+
+exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
+ ret void
+}
+!4 = metadata !{metadata !"branch_weights", i32 1, i32 1}
+!5 = metadata !{metadata !"branch_weights", i32 3, i32 1}
+
+; Two unrelated irreducible SCCs.
+define void @two_sccs(i1 %x) {
+; CHECK-LABEL: Printing analysis {{.*}} for function 'two_sccs':
+; CHECK-NEXT: block-frequency-info: two_sccs
+entry:
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
+ br i1 %x, label %a, label %b, !prof !6
+
+a:
+; CHECK-NEXT: a: float = 0.75,
+ br i1 %x, label %a.left, label %a.right, !prof !7
+
+a.left:
+; CHECK-NEXT: a.left: float = 1.5,
+ br i1 %x, label %a.right, label %exit, !prof !6
+
+a.right:
+; CHECK-NEXT: a.right: float = 1.5,
+ br i1 %x, label %a.left, label %exit, !prof !6
+
+b:
+; CHECK-NEXT: b: float = 0.25,
+ br i1 %x, label %b.left, label %b.right, !prof !7
+
+b.left:
+; CHECK-NEXT: b.left: float = 0.625,
+ br i1 %x, label %b.right, label %exit, !prof !8
+
+b.right:
+; CHECK-NEXT: b.right: float = 0.625,
+ br i1 %x, label %b.left, label %exit, !prof !8
+
+exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
+ ret void
+}
+!6 = metadata !{metadata !"branch_weights", i32 3, i32 1}
+!7 = metadata !{metadata !"branch_weights", i32 1, i32 1}
+!8 = metadata !{metadata !"branch_weights", i32 4, i32 1}
+
+; A true loop inside irreducible control flow.
+define void @loop_inside_irreducible(i1 %x) {
+; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_inside_irreducible':
+; CHECK-NEXT: block-frequency-info: loop_inside_irreducible
+entry:
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
+ br i1 %x, label %left, label %right, !prof !9
+
+left:
+; CHECK-NEXT: left: float = 2.0,
+ br i1 %x, label %right, label %exit, !prof !10
+
+right:
+; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]]
+ br label %loop
+
+loop:
+; CHECK-NEXT: loop: float = 6.0,
+ br i1 %x, label %loop, label %right.end, !prof !11
+
+right.end:
+; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]]
+ br i1 %x, label %left, label %exit, !prof !10
+
+exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
+ ret void
+}
+!9 = metadata !{metadata !"branch_weights", i32 1, i32 1}
+!10 = metadata !{metadata !"branch_weights", i32 3, i32 1}
+!11 = metadata !{metadata !"branch_weights", i32 2, i32 1}
+
+; Irreducible control flow in a branch that's in a true loop.
+define void @loop_around_branch_with_irreducible(i1 %x) {
+; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible':
+; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible
+entry:
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
+ br label %loop
+
+loop:
+; CHECK-NEXT: loop: float = 2.0, int = [[LOOP:[0-9]+]]
+ br i1 %x, label %normal, label %irreducible.entry, !prof !12
+
+normal:
+; CHECK-NEXT: normal: float = 1.5,
+ br label %loop.end
+
+irreducible.entry:
+; CHECK-NEXT: irreducible.entry: float = 0.5, int = [[IRREDUCIBLE:[0-9]+]]
+ br i1 %x, label %left, label %right, !prof !13
+
+left:
+; CHECK-NEXT: left: float = 1.0,
+ br i1 %x, label %right, label %irreducible.exit, !prof !12
+
+right:
+; CHECK-NEXT: right: float = 1.0,
+ br i1 %x, label %left, label %irreducible.exit, !prof !12
+
+irreducible.exit:
+; CHECK-NEXT: irreducible.exit: float = 0.5, int = [[IRREDUCIBLE]]
+ br label %loop.end
+
+loop.end:
+; CHECK-NEXT: loop.end: float = 2.0, int = [[LOOP]]
+ br i1 %x, label %loop, label %exit, !prof !13
+
+exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
+ ret void
+}
+!12 = metadata !{metadata !"branch_weights", i32 3, i32 1}
+!13 = metadata !{metadata !"branch_weights", i32 1, i32 1}
+
+; Irreducible control flow between two true loops.
+define void @loop_around_branch_with_irreducible_around_loop(i1 %x) {
+; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible_around_loop':
+; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible_around_loop
entry:
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
br label %loop
-; CHECK-NEXT: loop: float = [[HEAD:[0-9.]+]], int = [[HEADINT:[0-9]+]]
loop:
- br i1 %x, label %left, label %right
+; CHECK-NEXT: loop: float = 3.0, int = [[LOOP:[0-9]+]]
+ br i1 %x, label %normal, label %irreducible, !prof !14
+
+normal:
+; CHECK-NEXT: normal: float = 2.0,
+ br label %loop.end
+
+irreducible:
+; CHECK-NEXT: irreducible: float = 1.0,
+ br i1 %x, label %left, label %right, !prof !15
-; CHECK-NEXT: left:
left:
- br i1 %x, label %right, label %loop.end
+; CHECK-NEXT: left: float = 2.0,
+ br i1 %x, label %right, label %loop.end, !prof !16
-; CHECK-NEXT: right:
right:
- br i1 %x, label %left, label %loop.end
+; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]]
+ br label %right.loop
+
+right.loop:
+; CHECK-NEXT: right.loop: float = 10.0,
+ br i1 %x, label %right.loop, label %right.end, !prof !17
+
+right.end:
+; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]]
+ br i1 %x, label %left, label %loop.end, !prof !16
-; CHECK-NEXT: loop.end: float = [[HEAD]], int = [[HEADINT]]
loop.end:
- br i1 %x, label %loop, label %exit
+; CHECK-NEXT: loop.end: float = 3.0, int = [[LOOP]]
+ br i1 %x, label %loop, label %exit, !prof !14
+
+exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
+ ret void
+}
+!14 = metadata !{metadata !"branch_weights", i32 2, i32 1}
+!15 = metadata !{metadata !"branch_weights", i32 1, i32 1}
+!16 = metadata !{metadata !"branch_weights", i32 3, i32 1}
+!17 = metadata !{metadata !"branch_weights", i32 4, i32 1}
+
+; An irreducible SCC with a non-header.
+define void @nonheader(i1 %x) {
+; CHECK-LABEL: Printing analysis {{.*}} for function 'nonheader':
+; CHECK-NEXT: block-frequency-info: nonheader
+entry:
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
+ br i1 %x, label %left, label %right, !prof !18
+
+left:
+; CHECK-NEXT: left: float = 1.0,
+ br i1 %x, label %bottom, label %exit, !prof !19
+
+right:
+; CHECK-NEXT: right: float = 1.0,
+ br i1 %x, label %bottom, label %exit, !prof !20
+
+bottom:
+; CHECK-NEXT: bottom: float = 1.0,
+ br i1 %x, label %left, label %right, !prof !18
-; CHECK-NEXT: float = 1.0, int = [[ENTRY]]
exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
+ ret void
+}
+!18 = metadata !{metadata !"branch_weights", i32 1, i32 1}
+!19 = metadata !{metadata !"branch_weights", i32 1, i32 3}
+!20 = metadata !{metadata !"branch_weights", i32 3, i32 1}
+
+; An irreducible SCC with an irreducible sub-SCC. In the current version of
+; -block-freq, this means an extra header.
+;
+; This testcases uses non-trivial branch weights. The CHECK statements here
+; will start to fail if we change -block-freq to be more accurate. Currently,
+; we expect left, right and top to be treated as equal headers.
+define void @nonentry_header(i1 %x, i2 %y) {
+; CHECK-LABEL: Printing analysis {{.*}} for function 'nonentry_header':
+; CHECK-NEXT: block-frequency-info: nonentry_header
+entry:
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
+ br i1 %x, label %left, label %right, !prof !21
+
+left:
+; CHECK-NEXT: left: float = 3.0,
+ br i1 %x, label %top, label %bottom, !prof !22
+
+right:
+; CHECK-NEXT: right: float = 3.0,
+ br i1 %x, label %top, label %bottom, !prof !22
+
+top:
+; CHECK-NEXT: top: float = 3.0,
+ switch i2 %y, label %exit [ i2 0, label %left
+ i2 1, label %right
+ i2 2, label %bottom ], !prof !23
+
+bottom:
+; CHECK-NEXT: bottom: float = 4.5,
+ br label %top
+
+exit:
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
ret void
}
+!21 = metadata !{metadata !"branch_weights", i32 2, i32 1}
+!22 = metadata !{metadata !"branch_weights", i32 1, i32 1}
+!23 = metadata !{metadata !"branch_weights", i32 8, i32 1, i32 3, i32 12}
projects / oota-llvm.git / blobdiff