[PATCH] D38369: [InstSimplify] teach SimplifySelectInst() to fold more vector selects

[Haicheng Wu via Phabricator via llvm-commits]

haicheng created this revision.
Herald added a subscriber: mcrosier.

Call ConstantExpr::getSelect() to fold cases like below

`select <2 x i1><i1 true, i1 false>, <2 x i8> <i8 0, i8 1>, <2 x i8> <i8 2, i8 3>`

All operands are constants and the condition has mixed true and false conditions


Repository:
  rL LLVM

https://reviews.llvm.org/D38369

Files:
  lib/Analysis/InstructionSimplify.cpp
  test/Transforms/InstSimplify/select.ll


Index: test/Transforms/InstSimplify/select.ll
===================================================================
--- test/Transforms/InstSimplify/select.ll
+++ test/Transforms/InstSimplify/select.ll
@@ -17,6 +17,14 @@
   ret <2 x i8> %s
 }
 
+define <2 x i8> @vsel_mixedvec() {
+; CHECK-LABEL: @vsel_mixedvec(
+; CHECK-NEXT:    ret <2 x i8> <i8 0, i8 3>
+;
+  %s = select <2 x i1><i1 true, i1 false>, <2 x i8> <i8 0, i8 1>, <2 x i8> <i8 2, i8 3>
+  ret <2 x i8> %s
+}
+
 define i32 @test1(i32 %x) {
 ; CHECK-LABEL: @test1(
 ; CHECK-NEXT:    ret i32 %x
Index: lib/Analysis/InstructionSimplify.cpp
===================================================================
--- lib/Analysis/InstructionSimplify.cpp
+++ lib/Analysis/InstructionSimplify.cpp
@@ -3580,6 +3580,9 @@
   // select true, X, Y  -> X
   // select false, X, Y -> Y
   if (Constant *CB = dyn_cast<Constant>(CondVal)) {
+    if (Constant *CT = dyn_cast<Constant>(TrueVal))
+      if (Constant *CF = dyn_cast<Constant>(FalseVal))
+        return ConstantExpr::getSelect(CB, CT, CF);
     if (CB->isAllOnesValue())
       return TrueVal;
     if (CB->isNullValue())


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