[PATCH] D22511: [InstCombine] Enable cast-folding in logic(cast(icmp), cast(icmp))

[Matthias J. Reisinger via llvm-commits]

mreisinger updated this revision to Diff 64510.
mreisinger added a comment.

Thank you, I updated the test cases accordingly.


https://reviews.llvm.org/D22511

Files:
  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  test/Transforms/InstCombine/zext.ll

Index: test/Transforms/InstCombine/zext.ll
===================================================================
--- test/Transforms/InstCombine/zext.ll
+++ test/Transforms/InstCombine/zext.ll
@@ -73,3 +73,41 @@
   ret <2 x i64> %zext2
 }
 
+; Assert that zexts in logic(zext(icmp), zext(icmp)) can be folded
+; CHECK-LABEL: @fold_logic_zext_icmp(
+; CHECK-NEXT:    [[ICMP1:%.*]] = icmp sgt i64 %a, %b
+; CHECK-NEXT:    [[ICMP2:%.*]] = icmp slt i64 %a, %c
+; CHECK-NEXT:    [[AND:%.*]] = and i1 [[ICMP1]], [[ICMP2]]
+; CHECK-NEXT:    [[ZEXT:%.*]] = zext i1 [[AND]] to i8
+; CHECK-NEXT:    ret i8 [[ZEXT]]
+define i8 @fold_logic_zext_icmp(i64 %a, i64 %b, i64 %c) {
+  %1 = icmp sgt i64 %a, %b
+  %2 = zext i1 %1 to i8
+  %3 = icmp slt i64 %a, %c
+  %4 = zext i1 %3 to i8
+  %5 = and i8 %2, %4
+  ret i8 %5
+}
+
+; Assert that zexts in logic(zext(icmp), zext(icmp)) are also folded accross
+; nested logical operators.
+; CHECK-LABEL: @fold_nested_logic_zext_icmp(
+; CHECK-NEXT:    [[ICMP1:%.*]] = icmp sgt i64 %a, %b
+; CHECK-NEXT:    [[ICMP2:%.*]] = icmp slt i64 %a, %c
+; CHECK-NEXT:    [[AND:%.*]] = and i1 [[ICMP1]], [[ICMP2]]
+; CHECK-NEXT:    [[ICMP3:%.*]] = icmp eq i64 %a, %d
+; CHECK-NEXT:    [[OR:%.*]] = or i1 [[AND]], [[ICMP3]]
+; CHECK-NEXT:    [[ZEXT:%.*]] = zext i1 [[OR]] to i8
+; CHECK-NEXT:    ret i8 [[ZEXT]]
+define i8 @fold_nested_logic_zext_icmp(i64 %a, i64 %b, i64 %c, i64 %d) {
+  %1 = icmp sgt i64 %a, %b
+  %2 = zext i1 %1 to i8
+  %3 = icmp slt i64 %a, %c
+  %4 = zext i1 %3 to i8
+  %5 = and i8 %2, %4
+  %6 = icmp eq i64 %a, %d
+  %7 = zext i1 %6 to i8
+  %8 = or i8 %5, %7
+  ret i8 %8
+}
+
Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1212,6 +1212,13 @@
       isa<CmpInst>(CastSrc) && CI->getDestTy()->isVectorTy())
     return false;
 
+  // Don't optimize the cast if it is a (zext icmp) that can already be
+  // eliminated.
+  if (auto *ZExt = dyn_cast<ZExtInst>(CI))
+    if (auto *ICmp = dyn_cast<ICmpInst>(CastSrc))
+      if (transformZExtICmp(ICmp, *ZExt, false))
+        return false;
+
   return true;
 }
 
@@ -1260,8 +1267,7 @@
   Value *Cast1Src = Cast1->getOperand(0);
 
   // fold logic(cast(A), cast(B)) -> cast(logic(A, B))
-  if ((!isa<ICmpInst>(Cast0Src) || !isa<ICmpInst>(Cast1Src)) &&
-      shouldOptimizeCast(Cast0) && shouldOptimizeCast(Cast1)) {
+  if (shouldOptimizeCast(Cast0) && shouldOptimizeCast(Cast1)) {
     Value *NewOp = Builder->CreateBinOp(LogicOpc, Cast0Src, Cast1Src,
                                         I.getName());
     return CastInst::Create(CastOpcode, NewOp, DestTy);


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