[llvm] r307554 - Fix invalid cast in instcombine UMul/ZExt idiom

[Serge Guelton via llvm-commits]

Author: serge_sans_paille
Date: Mon Jul 10 09:51:40 2017
New Revision: 307554

URL: http://llvm.org/viewvc/llvm-project?rev=307554&view=rev
Log:
Fix invalid cast in instcombine UMul/ZExt idiom

Fixes https://bugs.llvm.org/show_bug.cgi?id=25454

Do not assume IRBuilder creates Instruction where it can create Value.
Do not assume idiom operands are constant, leave generalisation ot the IRBuilder.

Differential Revision: https://reviews.llvm.org/D35114

Added:
    llvm/trunk/test/Transforms/InstCombine/2017-07-07-UMul-ZExt.ll
Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=307554&r1=307553&r2=307554&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Mon Jul 10 09:51:40 2017
@@ -3856,17 +3856,18 @@ static Instruction *processUMulZExtIdiom
       } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
         assert(BO->getOpcode() == Instruction::And);
         // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
-        ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
-        APInt ShortMask = CI->getValue().trunc(MulWidth);
+        Value *ShortMask =
+            Builder.CreateTrunc(BO->getOperand(1), Builder.getIntNTy(MulWidth));
         Value *ShortAnd = Builder.CreateAnd(Mul, ShortMask);
-        Instruction *Zext =
-            cast<Instruction>(Builder.CreateZExt(ShortAnd, BO->getType()));
-        IC.Worklist.Add(Zext);
+        Value *Zext = Builder.CreateZExt(ShortAnd, BO->getType());
+        if (auto *ZextI = dyn_cast<Instruction>(Zext))
+          IC.Worklist.Add(ZextI);
         IC.replaceInstUsesWith(*BO, Zext);
       } else {
         llvm_unreachable("Unexpected Binary operation");
       }
-      IC.Worklist.Add(cast<Instruction>(U));
+      if (auto *UI = dyn_cast<Instruction>(U))
+        IC.Worklist.Add(UI);
     }
   }
   if (isa<Instruction>(OtherVal))

Added: llvm/trunk/test/Transforms/InstCombine/2017-07-07-UMul-ZExt.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/2017-07-07-UMul-ZExt.ll?rev=307554&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/2017-07-07-UMul-ZExt.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/2017-07-07-UMul-ZExt.ll Mon Jul 10 09:51:40 2017
@@ -0,0 +1,29 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; CHECK: llvm.umul.with.overflow
+define i32 @sterix(i32, i8, i64) {
+entry:
+  %conv = zext i32 %0 to i64
+  %conv1 = sext i8 %1 to i32
+  %mul = mul i32 %conv1, 1945964878
+  %sh_prom = trunc i64 %2 to i32
+  %shr = lshr i32 %mul, %sh_prom
+  %conv2 = zext i32 %shr to i64
+  %mul3 = mul nuw nsw i64 %conv, %conv2
+  %conv6 = and i64 %mul3, 4294967295
+  %tobool = icmp ne i64 %conv6, %mul3
+  br i1 %tobool, label %lor.end, label %lor.rhs
+
+lor.rhs:
+  %and = and i64 %2, %mul3
+  %conv4 = trunc i64 %and to i32
+  %tobool7 = icmp ne i32 %conv4, 0
+  %lnot = xor i1 %tobool7, true
+  br label %lor.end
+
+lor.end:
+  %3 = phi i1 [ true, %entry ], [ %lnot, %lor.rhs ]
+  %conv8 = zext i1 %3 to i32
+  ret i32 %conv8
+}
+