[InstCombine] use constant pattern matchers with icmp+sext

The previous code worked with vectors, but it failed when the
vector constants contained undef elements. 
The matchers handle those cases.

llvm-svn: 335262

1 files changed, 11 insertions, 14 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index aa86dddf04d..42828eaeb2b 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1191,22 +1191,19 @@ Instruction *InstCombiner::transformSExtICmp(ICmpInst *ICI, Instruction &CI) {
   if (!Op1->getType()->isIntOrIntVectorTy())
     return nullptr;
 
-  if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
+  if ((Pred == ICmpInst::ICMP_SLT && match(Op1, m_ZeroInt())) ||
+      (Pred == ICmpInst::ICMP_SGT && match(Op1, m_AllOnes()))) {
     // (x <s  0) ? -1 : 0 -> ashr x, 31        -> all ones if negative
     // (x >s -1) ? -1 : 0 -> not (ashr x, 31)  -> all ones if positive
-    if ((Pred == ICmpInst::ICMP_SLT && Op1C->isNullValue()) ||
-        (Pred == ICmpInst::ICMP_SGT && Op1C->isAllOnesValue())) {
-
-      Value *Sh = ConstantInt::get(Op0->getType(),
-                                   Op0->getType()->getScalarSizeInBits()-1);
-      Value *In = Builder.CreateAShr(Op0, Sh, Op0->getName() + ".lobit");
-      if (In->getType() != CI.getType())
-        In = Builder.CreateIntCast(In, CI.getType(), true /*SExt*/);
-
-      if (Pred == ICmpInst::ICMP_SGT)
-        In = Builder.CreateNot(In, In->getName() + ".not");
-      return replaceInstUsesWith(CI, In);
-    }
+    Value *Sh = ConstantInt::get(Op0->getType(),
+                                 Op0->getType()->getScalarSizeInBits() - 1);
+    Value *In = Builder.CreateAShr(Op0, Sh, Op0->getName() + ".lobit");
+    if (In->getType() != CI.getType())
+      In = Builder.CreateIntCast(In, CI.getType(), true /*SExt*/);
+
+    if (Pred == ICmpInst::ICMP_SGT)
+      In = Builder.CreateNot(In, In->getName() + ".not");
+    return replaceInstUsesWith(CI, In);
   }
 
   if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {