Reorders two transforms that collide with each other

One performs: (X == 13 | X == 14) -> X-13 <u 2
The other: (A == C1 || A == C2) -> (A & ~(C1 ^ C2)) == C1

The problem is that there are certain values of C1 and C2 that
trigger both transforms but the first one blocks out the second,
this generates suboptimal code.

Reordering the transforms should be better in every case and
allows us to do interesting stuff like turn:
  %shr = lshr i32 %X, 4
  %and = and i32 %shr, 15
  %add = add i32 %and, -14
  %tobool = icmp ne i32 %add, 0

into:
  %and = and i32 %X, 240
  %tobool = icmp ne i32 %and, 224

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179493 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index a7f01494874b9fbf6e155db000348c06746506d4..ec75dd2e0425809b21cc9fd2a1ddbd89950c567b 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1547,14 +1547,6 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
     switch (RHSCC) {
     default: llvm_unreachable("Unknown integer condition code!");
     case ICmpInst::ICMP_EQ:
-      if (LHSCst == SubOne(RHSCst)) {
-        // (X == 13 | X == 14) -> X-13 <u 2
-        Constant *AddCST = ConstantExpr::getNeg(LHSCst);
-        Value *Add = Builder->CreateAdd(Val, AddCST, Val->getName()+".off");
-        AddCST = ConstantExpr::getSub(AddOne(RHSCst), LHSCst);
-        return Builder->CreateICmpULT(Add, AddCST);
-      }
-
       if (LHS->getOperand(0) == RHS->getOperand(0)) {
         // if LHSCst and RHSCst differ only by one bit:
         // (A == C1 || A == C2) -> (A & ~(C1 ^ C2)) == C1
@@ -1568,6 +1560,14 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
         }
       }
 
+      if (LHSCst == SubOne(RHSCst)) {
+        // (X == 13 | X == 14) -> X-13 <u 2
+        Constant *AddCST = ConstantExpr::getNeg(LHSCst);
+        Value *Add = Builder->CreateAdd(Val, AddCST, Val->getName()+".off");
+        AddCST = ConstantExpr::getSub(AddOne(RHSCst), LHSCst);
+        return Builder->CreateICmpULT(Add, AddCST);
+      }
+
       break;                         // (X == 13 | X == 15) -> no change
     case ICmpInst::ICMP_UGT:         // (X == 13 | X u> 14) -> no change
     case ICmpInst::ICMP_SGT:         // (X == 13 | X s> 14) -> no change

diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll
index 74adbba42b48b1278669cd52230ed9f2beee35de..c912a576c3d29a4f03065a56464d426788f5a3df 100644 (file)
--- a/test/Transforms/InstCombine/icmp.ll
+++ b/test/Transforms/InstCombine/icmp.ll
@@ -964,3 +964,15 @@ define i1 @icmp_and_shl_neg_eq_0(i32 %A, i32 %B) {
   %cmp = icmp eq i32 %and, 0
   ret i1 %cmp
 }
+
+; CHECK: @icmp_add_and_shr_ne_0
+; CHECK-NEXT: [[AND:%[a-z0-9]+]] = and i32 %X, 240
+; CHECK-NEXT: [[CMP:%[a-z0-9]+]] = icmp ne i32 [[AND]], 224
+; CHECK-NEXT: ret i1 [[CMP]]
+define i1 @icmp_add_and_shr_ne_0(i32 %X) {
+  %shr = lshr i32 %X, 4
+  %and = and i32 %shr, 15
+  %add = add i32 %and, -14
+  %tobool = icmp ne i32 %add, 0
+  ret i1 %tobool
+}

diff --git a/test/Transforms/InstCombine/load-cmp.ll b/test/Transforms/InstCombine/load-cmp.ll
index d88188e4109cdd9e66066c0eab7cdaa48fd0b202..869215cb58d47f9cb7e8093d1212a688063d3165 100644 (file)
--- a/test/Transforms/InstCombine/load-cmp.ll
+++ b/test/Transforms/InstCombine/load-cmp.ll
@@ -100,8 +100,8 @@ define i1 @test8(i32 %X) {
   %S = icmp eq i16 %R, 0
   ret i1 %S
 ; CHECK: @test8
-; CHECK-NEXT: add i32 %X, -8
-; CHECK-NEXT: icmp ult i32 {{.*}}, 2
+; CHECK-NEXT: and i32 %X, -2
+; CHECK-NEXT: icmp eq i32 {{.*}}, 8
 ; CHECK-NEXT: ret i1
 }
 

diff --git a/test/Transforms/InstCombine/or.ll b/test/Transforms/InstCombine/or.ll
index bde2a54048adddc8c502cb06668eeec31ad3f5ec..7226bd93996f0e77c2cc049dc4b3667fcef232b8 100644 (file)
--- a/test/Transforms/InstCombine/or.ll
+++ b/test/Transforms/InstCombine/or.ll
@@ -178,12 +178,12 @@ define i1 @test18(i32 %A) {
 define i1 @test19(i32 %A) {
         %B = icmp eq i32 %A, 50
         %C = icmp eq i32 %A, 51
-        ;; (A-50) < 2
+        ;; (A&-2) == 50
         %D = or i1 %B, %C
         ret i1 %D
 ; CHECK: @test19
-; CHECK: add i32
-; CHECK: icmp ult 
+; CHECK: and i32
+; CHECK: icmp eq 
 ; CHECK: ret i1
 }