Improve instcombine's handling of integer min and max in two ways:

 - Recognize expressions like "x > -1 ? x : 0" as min/max and turn them
   into expressions like "x < 0 ? 0 : x", which is easily recognizable
   as a min/max operation.
 - Refrain from folding expression like "y/2 < 1" to "y < 2" when the
   comparison is being used as part of a min or max idiom, like
   "y/2 < 1 ? 1 : y/2". In that case, the division has another use, so
   folding doesn't eliminate it, and obfuscates the min/max, making it
   harder to recognize as a min/max operation.

These benefit ScalarEvolution, CodeGen, and anything else that wants to
recognize integer min and max.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56246 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 5 deletions

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 60980d26aa..4e85e90e9e 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -1831,11 +1831,6 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
   case Instruction::Select:
     // This could be a smax or umax that was lowered earlier.
     // Try to recover it.
-    //
-    // FIXME: This doesn't recognize code like this:
-    //    %t = icmp sgt i32 %n, -1
-    //    %max = select i1 %t, i32 %n, i32 0
-    //
     if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
       Value *LHS = ICI->getOperand(0);
       Value *RHS = ICI->getOperand(1);