[PATCH] D11577: Reassociate: Implement isUnmovableInstruction() without a hardcoded list
Matthias Braun
matze at braunis.de
Tue Jul 28 16:33:39 PDT 2015
MatzeB updated the summary for this revision.
MatzeB updated this revision to Diff 30874.
MatzeB added a comment.
Updated the patch to use a !I->mayRead() && isSafeToSpeculativelyExecute(I) to determine whether we can move an instruction around.
Repository:
rL LLVM
http://reviews.llvm.org/D11577
Files:
lib/Transforms/Scalar/Reassociate.cpp
test/Transforms/Reassociate/vaarg_movable.ll
Index: test/Transforms/Reassociate/vaarg_movable.ll
===================================================================
--- /dev/null
+++ test/Transforms/Reassociate/vaarg_movable.ll
@@ -0,0 +1,28 @@
+; RUN: opt -S -reassociate -die < %s | FileCheck %s
+
+; The two va_arg instructions depend on the memory/context, are therfore not
+; identical and the sub should not be optimized to 0 by reassociate.
+;
+; CHECK-LABEL @func(
+; ...
+; CHECK: %v0 = va_arg i8** %varargs, i32
+; CHECK: %v1 = va_arg i8** %varargs, i32
+; CHECK: %v0.neg = sub i32 0, %v0
+; CHECK: %sub = add i32 %v0.neg, 1
+; CHECK: %add = add i32 %sub, %v1
+; ...
+; CHECK: ret i32 %add
+define i32 @func(i32 %dummy, ...) {
+ %varargs = alloca i8*, align 8
+ %varargs1 = bitcast i8** %varargs to i8*
+ call void @llvm.va_start(i8* %varargs1)
+ %v0 = va_arg i8** %varargs, i32
+ %v1 = va_arg i8** %varargs, i32
+ %sub = sub nsw i32 %v1, %v0
+ %add = add nsw i32 %sub, 1
+ call void @llvm.va_end(i8* %varargs1)
+ ret i32 %add
+}
+
+declare void @llvm.va_start(i8*)
+declare void @llvm.va_end(i8*)
Index: lib/Transforms/Scalar/Reassociate.cpp
===================================================================
--- lib/Transforms/Scalar/Reassociate.cpp
+++ lib/Transforms/Scalar/Reassociate.cpp
@@ -26,6 +26,7 @@
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
@@ -255,27 +256,6 @@
return nullptr;
}
-static bool isUnmovableInstruction(Instruction *I) {
- switch (I->getOpcode()) {
- case Instruction::PHI:
- case Instruction::LandingPad:
- case Instruction::Alloca:
- case Instruction::Load:
- case Instruction::Invoke:
- case Instruction::UDiv:
- case Instruction::SDiv:
- case Instruction::FDiv:
- case Instruction::URem:
- case Instruction::SRem:
- case Instruction::FRem:
- return true;
- case Instruction::Call:
- return !isa<DbgInfoIntrinsic>(I);
- default:
- return false;
- }
-}
-
void Reassociate::BuildRankMap(Function &F) {
unsigned i = 2;
@@ -295,7 +275,7 @@
// we cannot move. This ensures that the ranks for these instructions are
// all different in the block.
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
- if (isUnmovableInstruction(I))
+ if (I->mayReadOrWriteMemory() || !isSafeToSpeculativelyExecute(I))
ValueRankMap[&*I] = ++BBRank;
}
}
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