Get rid of an incorrect optimization for shuffles with PALIGNR and simplify isPALIGNR...

Addresses PR10466, although the crash from that PR only triggers in cases where DAGCombine misses optimizing a shuffle.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135980 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index c3fa9d1fa2deeb572f09d3bd7e63e64dcac7f705..d2c8778debd1be248ff7c4d00d694b9fd112d65e 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -3075,27 +3075,16 @@ static bool isPALIGNRMask(const SmallVectorImpl<int> &Mask, EVT VT,
   if (i == e)
     return false;
 
-  // Determine if it's ok to perform a palignr with only the LHS, since we
-  // don't have access to the actual shuffle elements to see if RHS is undef.
-  bool Unary = Mask[i] < (int)e;
-  bool NeedsUnary = false;
+  // Make sure we're shifting in the right direction.
+  if (Mask[i] <= i)
+    return false;
 
   int s = Mask[i] - i;
 
   // Check the rest of the elements to see if they are consecutive.
   for (++i; i != e; ++i) {
     int m = Mask[i];
-    if (m < 0)
-      continue;
-
-    Unary = Unary && (m < (int)e);
-    NeedsUnary = NeedsUnary || (m < s);
-
-    if (NeedsUnary && !Unary)
-      return false;
-    if (Unary && m != ((s+i) & (e-1)))
-      return false;
-    if (!Unary && m != (s+i))
+    if (m >= 0 && m != s+i)
       return false;
   }
   return true;
@@ -3631,6 +3620,7 @@ unsigned X86::getShufflePALIGNRImmediate(SDNode *N) {
     if (Val >= 0)
       break;
   }
+  assert(Val - i > 0 && "PALIGNR imm should be positive");
   return (Val - i) * EltSize;
 }
 

diff --git a/test/CodeGen/X86/palignr.ll b/test/CodeGen/X86/palignr.ll
index 3812c7238c43c840e8e99030ce93e2faa5abf22f..ddcb05c97032da6c43dc8cfb6cec8a6bb2e3fd2d 100644 (file)
--- a/test/CodeGen/X86/palignr.ll
+++ b/test/CodeGen/X86/palignr.ll
@@ -2,6 +2,7 @@
 ; RUN: llc < %s -march=x86 -mcpu=yonah | FileCheck --check-prefix=YONAH %s
 
 define <4 x i32> @test1(<4 x i32> %A, <4 x i32> %B) nounwind {
+; CHECK: test1:
 ; CHECK: pshufd
 ; CHECK-YONAH: pshufd
   %C = shufflevector <4 x i32> %A, <4 x i32> undef, <4 x i32> < i32 1, i32 2, i32 3, i32 0 >
@@ -9,6 +10,7 @@ define <4 x i32> @test1(<4 x i32> %A, <4 x i32> %B) nounwind {
 }
 
 define <4 x i32> @test2(<4 x i32> %A, <4 x i32> %B) nounwind {
+; CHECK: test2:
 ; CHECK: palignr
 ; CHECK-YONAH: shufps
   %C = shufflevector <4 x i32> %A, <4 x i32> %B, <4 x i32> < i32 1, i32 2, i32 3, i32 4 >
@@ -16,43 +18,56 @@ define <4 x i32> @test2(<4 x i32> %A, <4 x i32> %B) nounwind {
 }
 
 define <4 x i32> @test3(<4 x i32> %A, <4 x i32> %B) nounwind {
+; CHECK: test3:
 ; CHECK: palignr
   %C = shufflevector <4 x i32> %A, <4 x i32> %B, <4 x i32> < i32 1, i32 2, i32 undef, i32 4 >
        ret <4 x i32> %C
 }
 
 define <4 x i32> @test4(<4 x i32> %A, <4 x i32> %B) nounwind {
+; CHECK: test4:
 ; CHECK: palignr
   %C = shufflevector <4 x i32> %A, <4 x i32> %B, <4 x i32> < i32 6, i32 7, i32 undef, i32 1 >
        ret <4 x i32> %C
 }
 
 define <4 x float> @test5(<4 x float> %A, <4 x float> %B) nounwind {
+; CHECK: test5:
 ; CHECK: palignr
   %C = shufflevector <4 x float> %A, <4 x float> %B, <4 x i32> < i32 6, i32 7, i32 undef, i32 1 >
        ret <4 x float> %C
 }
 
 define <8 x i16> @test6(<8 x i16> %A, <8 x i16> %B) nounwind {
+; CHECK: test6:
 ; CHECK: palignr
   %C = shufflevector <8 x i16> %A, <8 x i16> %B, <8 x i32> < i32 3, i32 4, i32 undef, i32 6, i32 7, i32 8, i32 9, i32 10 >
        ret <8 x i16> %C
 }
 
 define <8 x i16> @test7(<8 x i16> %A, <8 x i16> %B) nounwind {
+; CHECK: test7:
 ; CHECK: palignr
   %C = shufflevector <8 x i16> %A, <8 x i16> %B, <8 x i32> < i32 undef, i32 6, i32 undef, i32 8, i32 9, i32 10, i32 11, i32 12 >
        ret <8 x i16> %C
 }
 
-define <8 x i16> @test8(<8 x i16> %A, <8 x i16> %B) nounwind {
-; CHECK: palignr
-  %C = shufflevector <8 x i16> %A, <8 x i16> %B, <8 x i32> < i32 undef, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 0 >
-       ret <8 x i16> %C
-}
-
-define <16 x i8> @test9(<16 x i8> %A, <16 x i8> %B) nounwind {
+define <16 x i8> @test8(<16 x i8> %A, <16 x i8> %B) nounwind {
+; CHECK: test8:
 ; CHECK: palignr
   %C = shufflevector <16 x i8> %A, <16 x i8> %B, <16 x i32> < i32 5, i32 6, i32 7, i32 undef, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 16, i32 17, i32 18, i32 19, i32 20 >
        ret <16 x i8> %C
 }
+
+; Check that we don't do unary (circular on single operand) palignr incorrectly.
+; (It is possible, but before this testcase was committed, it was being done
+; incorrectly.  In particular, one of the operands of the palignr node
+; was an UNDEF.)
+define <8 x i16> @test9(<8 x i16> %A, <8 x i16> %B) nounwind {
+; CHECK: test9:
+; CHECK-NOT: palignr
+; CHECK: pshufb
+  %C = shufflevector <8 x i16> %B, <8 x i16> %A, <8 x i32> < i32 undef, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 0 >
+       ret <8 x i16> %C
+}
+