[PATCH] D149077: [InstCombine] Add !noundef if is guaranteed do not violate !range

[luxufan via Phabricator via llvm-commits]

StephenFan updated this revision to Diff 516625.
StephenFan added a comment.

If the instruction self can create poison or undef, it is not guaranteed do not violate the !range metadata


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D149077/new/

https://reviews.llvm.org/D149077

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/InstCombine/ctpop.ll
  llvm/test/Transforms/InstCombine/cttz.ll


Index: llvm/test/Transforms/InstCombine/cttz.ll
===================================================================
--- llvm/test/Transforms/InstCombine/cttz.ll
+++ llvm/test/Transforms/InstCombine/cttz.ll
@@ -118,3 +118,25 @@
   %tz = tail call <2 x i64> @llvm.cttz.v2i64(<2 x i64> %s, i1 false)
   ret <2 x i64> %tz
 }
+
+define i32 @cttz_arg_noundef_zero_poison(i16 noundef %x) {
+; CHECK-LABEL: @cttz_arg_noundef_zero_poison(
+; CHECK-NEXT:    [[TMP1:%.*]] = call i16 @llvm.cttz.i16(i16 [[X:%.*]], i1 true), !range [[RNG0]]
+; CHECK-NEXT:    [[TZ:%.*]] = zext i16 [[TMP1]] to i32
+; CHECK-NEXT:    ret i32 [[TZ]]
+;
+  %z = zext i16 %x to i32
+  %tz = call i32 @llvm.cttz.i32(i32 %z, i1 true)
+  ret i32 %tz
+}
+
+define i32 @cttz_arg_noundef(i16 noundef %x) {
+; CHECK-LABEL: @cttz_arg_noundef(
+; CHECK-NEXT:    [[Z:%.*]] = zext i16 [[X:%.*]] to i32
+; CHECK-NEXT:    [[TZ:%.*]] = call i32 @llvm.cttz.i32(i32 [[Z]], i1 false), !range [[RNG1]], !noundef !3
+; CHECK-NEXT:    ret i32 [[TZ]]
+;
+  %z = zext i16 %x to i32
+  %tz = call i32 @llvm.cttz.i32(i32 %z, i1 false)
+  ret i32 %tz
+}
Index: llvm/test/Transforms/InstCombine/ctpop.ll
===================================================================
--- llvm/test/Transforms/InstCombine/ctpop.ll
+++ llvm/test/Transforms/InstCombine/ctpop.ll
@@ -475,3 +475,12 @@
   %i5 = xor i32 %i2, %i4
   ret i32 %i5
 }
+
+define i8 @arg_noundef(i8 noundef %arg) {
+; CHECK-LABEL: @arg_noundef(
+; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctpop.i8(i8 [[ARG:%.*]]), !range [[RNG0]], !noundef !6
+; CHECK-NEXT:    ret i8 [[CNT]]
+;
+  %cnt = call i8 @llvm.ctpop.i8(i8 %arg)
+  ret i8 %cnt
+}
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -505,6 +505,21 @@
   return cast<Instruction>(Result);
 }
 
+static bool isGuaranteedDoNotViolateRangeMetadata(Instruction *I,
+                                                  unsigned KnownMin,
+                                                  unsigned KnownMax) {
+  if (MDNode *Node = I->getMetadata(LLVMContext::MD_range))
+    if (mdconst::extract<ConstantInt>(Node->getOperand(0))
+            ->equalsInt(KnownMin) &&
+        mdconst::extract<ConstantInt>(Node->getOperand(1))->equalsInt(KnownMax))
+      if (!canCreateUndefOrPoison(cast<Operator>(I),
+                                  /*ConsiderFlagsAndMetadata*/ false) &&
+          all_of(I->operands(),
+                 [&](Value *V) { return isGuaranteedNotToBeUndefOrPoison(V); }))
+        return true;
+  return false;
+}
+
 static Instruction *foldCttzCtlz(IntrinsicInst &II, InstCombinerImpl &IC) {
   assert((II.getIntrinsicID() == Intrinsic::cttz ||
           II.getIntrinsicID() == Intrinsic::ctlz) &&
@@ -602,6 +617,12 @@
     return &II;
   }
 
+  if (!II.getMetadata(LLVMContext::MD_noundef) &&
+      isGuaranteedDoNotViolateRangeMetadata(&II, DefiniteZeros,
+                                            PossibleZeros + 1))
+    II.setMetadata(LLVMContext::MD_noundef,
+                   MDNode::get(II.getContext(), nullptr));
+
   return nullptr;
 }
 
@@ -683,6 +704,11 @@
     return &II;
   }
 
+  if (!II.getMetadata(LLVMContext::MD_noundef) &&
+      isGuaranteedDoNotViolateRangeMetadata(&II, MinCount, MaxCount + 1))
+    II.setMetadata(LLVMContext::MD_noundef,
+                   MDNode::get(II.getContext(), nullptr));
+
   return nullptr;
 }
 


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