Reapply r237453 with a fix for the test timeouts.

The test timeouts were due to instcombine fighting itself. Regression test added.
Original log message:

Canonicalize min/max expressions correctly.

This patch introduces a canonical form for min/max idioms where one operand
is extended or truncated. This often happens when the other operand is a
constant. For example:

  %1 = icmp slt i32 %a, i32 0
    %2 = sext i32 %a to i64
      %3 = select i1 %1, i64 %2, i64 0

Would now be canonicalized into:

  %1 = icmp slt i32 %a, i32 0
    %2 = select i1 %1, i32 %a, i32 0
      %3 = sext i32 %2 to i64

This builds upon a patch posted by David Majenemer
(https://www.marc.info/?l=llvm-commits&m=143008038714141&w=2). That pass
passively stopped instcombine from ruining canonical patterns. This
patch additionally actively makes instcombine canonicalize too.

Canonicalization of expressions involving a change in type from int->fp
or fp->int are not yet implemented.

llvm-svn: 237520

1 files changed, 18 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index b13d3ed..d2fbcdd 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1154,18 +1154,30 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
       }
 
   // See if we can fold the select into one of our operands.
-  if (SI.getType()->isIntegerTy()) {
+  if (SI.getType()->isIntOrIntVectorTy()) {
     if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
       return FoldI;
 
     Value *LHS, *RHS, *LHS2, *RHS2;
-    SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS);
+    Instruction::CastOps CastOp;
+    SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS, &CastOp);
 
-    // MAX(MAX(a, b), a) -> MAX(a, b)
-    // MIN(MIN(a, b), a) -> MIN(a, b)
-    // MAX(MIN(a, b), a) -> a
-    // MIN(MAX(a, b), a) -> a
     if (SPF) {
+      // Canonicalize so that type casts are outside select patterns.
+      if (LHS->getType()->getPrimitiveSizeInBits() !=
+          SI.getType()->getPrimitiveSizeInBits()) {
+        CmpInst::Predicate Pred = getICmpPredicateForMinMax(SPF);
+        Value *Cmp = Builder->CreateICmp(Pred, LHS, RHS);
+        Value *NewSI = Builder->CreateCast(CastOp,
+                                           Builder->CreateSelect(Cmp, LHS, RHS),
+                                           SI.getType());
+        return ReplaceInstUsesWith(SI, NewSI);
+      }
+
+      // MAX(MAX(a, b), a) -> MAX(a, b)
+      // MIN(MIN(a, b), a) -> MIN(a, b)
+      // MAX(MIN(a, b), a) -> a
+      // MIN(MAX(a, b), a) -> a
       if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2))
         if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
                                           SI, SPF, RHS))