[PATCH] D24565: [InstCombine] PR30366 : Teach the udiv folding logic how to handle constant expressions.
Andrea Di Biagio via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 14 10:42:16 PDT 2016
andreadb updated this revision to Diff 71392.
andreadb added a comment.
Patch updated.
Addressed David's review comments.
https://reviews.llvm.org/D24565
Files:
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
test/Transforms/InstCombine/udiv-simplify.ll
Index: test/Transforms/InstCombine/udiv-simplify.ll
===================================================================
--- test/Transforms/InstCombine/udiv-simplify.ll
+++ test/Transforms/InstCombine/udiv-simplify.ll
@@ -47,3 +47,18 @@
%z = sext i32 %r to i64
ret i64 %z
}
+
+; The udiv should be simplified according to the rule:
+; X udiv (C1 << N), where C1 is `1<<C2` --> X >> (N+C2)
+ at b = external global [1 x i16]
+
+define i32 @PR30366(i1 %a) {
+; CHECK-LABEL: @PR30366(
+; CHECK-NEXT: [[Z:%.*]] = zext i1 %a to i32
+; CHECK-NEXT: [[D:%.*]] = lshr i32 [[Z]], zext (i16 ptrtoint ([1 x i16]* @b to i16) to i32)
+; CHECK-NEXT: ret i32 [[D]]
+;
+ %z = zext i1 %a to i32
+ %d = udiv i32 %z, zext (i16 shl (i16 1, i16 ptrtoint ([1 x i16]* @b to i16)) to i32)
+ ret i32 %d
+}
Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -993,17 +993,19 @@
// X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
InstCombiner &IC) {
- Instruction *ShiftLeft = cast<Instruction>(Op1);
- if (isa<ZExtInst>(ShiftLeft))
- ShiftLeft = cast<Instruction>(ShiftLeft->getOperand(0));
-
- const APInt &CI =
- cast<Constant>(ShiftLeft->getOperand(0))->getUniqueInteger();
- Value *N = ShiftLeft->getOperand(1);
- if (CI != 1)
- N = IC.Builder->CreateAdd(N, ConstantInt::get(N->getType(), CI.logBase2()));
- if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
- N = IC.Builder->CreateZExt(N, Z->getDestTy());
+ Value *ShiftLeft = nullptr;
+ if (!match(Op1, m_ZExt(m_Value(ShiftLeft))))
+ ShiftLeft = Op1;
+
+ const APInt *CI;
+ Value *N;
+ if (!match(ShiftLeft, m_Shl(m_APInt(CI), m_Value(N))))
+ llvm_unreachable("match should never fail here!");
+ if (*CI != 1)
+ N = IC.Builder->CreateAdd(N,
+ ConstantInt::get(N->getType(), CI->logBase2()));
+ if (Op1 != ShiftLeft)
+ N = IC.Builder->CreateZExt(N, Op1->getType());
BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N);
if (I.isExact())
LShr->setIsExact();
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