[llvm-commits] [llvm] r121965 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCompares.cpp test/Transforms/InstCombine/overflow.ll
Duncan Sands
baldrick at free.fr
Thu Dec 16 01:40:54 PST 2010
Author: baldrick
Date: Thu Dec 16 03:40:54 2010
New Revision: 121965
URL: http://llvm.org/viewvc/llvm-project?rev=121965&view=rev
Log:
Speculatively revert commit 121905 since it looks like it might have broken the
dragonegg self-host buildbot. Original commit message:
Add an InstCombine transform to recognize instances of manual overflow-safe addition
(performing the addition in a wider type and explicitly checking for overflow), and
fold them down to intrinsics. This currently only supports signed-addition, but could
be generalized if someone works out the magic constant formulas for other operations.
Removed:
llvm/trunk/test/Transforms/InstCombine/overflow.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=121965&r1=121964&r2=121965&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Thu Dec 16 03:40:54 2010
@@ -1657,71 +1657,6 @@
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
Value *A = 0, *B = 0;
- // Match the following pattern, which is a common idiom when writing
- // overflow-safe integer arithmetic function. The source performs an
- // addition in wider type, and explicitly checks for overflow using
- // comparisons against INT_MIN and INT_MAX. Simplify this by using the
- // sadd_with_overflow intrinsic.
- // FIXME: This could probably be generalized to handle other overflow-safe
- // operations if we worked out the formulas to compute the appropriate
- // magic constants.
- //
- // INT64 : a, b, sum = a + b
- // if sum < INT32_MIN || sum > INT_MAX then
- // ...
- // else
- // ...
- {
- ConstantInt *CI2;
-
- // I = icmp ugt (add (add A B) CI2) CI
- if (I.getPredicate() == ICmpInst::ICMP_UGT &&
- match(Op0, m_Add(m_Add(m_Value(A), m_Value(B)),
- m_ConstantInt(CI2)))) {
- const IntegerType *WideType = cast<IntegerType>(CI->getType());
- unsigned WideWidth = WideType->getBitWidth();
- unsigned NarrowWidth = WideWidth / 2;
- const IntegerType *NarrowType =
- IntegerType::get(CI->getContext(), NarrowWidth);
-
- // NarrowAllOnes and NarrowSignBit are the magic constants used to
- // perform an overflow check in the wider type: 0x00..00FF..FF and
- // 0x00..0010..00 respectively, where the highest set bit in each is
- // what would be the sign bit in the narrower type.
- ConstantInt *NarrowAllOnes = cast<ConstantInt>(ConstantInt::get(WideType,
- APInt::getAllOnesValue(NarrowWidth).zext(WideWidth)));
- APInt SignBit(WideWidth, 0);
- SignBit.setBit(NarrowWidth-1);
- ConstantInt *NarrowSignBit =
- cast<ConstantInt>(ConstantInt::get(WideType, SignBit));
-
- if (CI == NarrowAllOnes && CI2 == NarrowSignBit) {
- Module *M = I.getParent()->getParent()->getParent();
-
- const Type *IntrinsicType = NarrowType;
- Value *F = Intrinsic::getDeclaration(M, Intrinsic::sadd_with_overflow,
- &IntrinsicType, 1);
-
- // If the pattern matches, truncate the inputs to the narrower type and
- // use the sadd_with_overflow intrinsic to efficiently compute both the
- // result and the overflow bit.
- Value *TruncA = Builder->CreateTrunc(A, NarrowType, A->getName());
- Value *TruncB = Builder->CreateTrunc(B, NarrowType, B->getName());
- CallInst *Call = Builder->CreateCall2(F, TruncA, TruncB);
- Value *Add = Builder->CreateExtractValue(Call, 0);
- Value *ZExt = Builder->CreateZExt(Add, WideType);
-
- // The inner add was the result of the narrow add, zero extended to the
- // wider type. Replace it with the result computed by the intrinsic.
- Instruction *OrigAdd =
- cast<Instruction>(cast<Instruction>(I.getOperand(0))->getOperand(0));
- OrigAdd->replaceAllUsesWith(ZExt);
-
- return ExtractValueInst::Create(Call, 1);
- }
- }
- }
-
// (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B)
if (I.isEquality() && CI->isZero() &&
match(Op0, m_Sub(m_Value(A), m_Value(B)))) {
Removed: llvm/trunk/test/Transforms/InstCombine/overflow.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/overflow.ll?rev=121964&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/overflow.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/overflow.ll (removed)
@@ -1,27 +0,0 @@
-; RUN: opt -S -instcombine < %s | FileCheck %s
-; <rdar://problem/8558713>
-
-; CHECK: @test1
-define i32 @test1(i32 %a, i32 %b) nounwind ssp {
-entry:
-; CHECK-NOT: sext
- %conv = sext i32 %a to i64
- %conv2 = sext i32 %b to i64
- %add = add nsw i64 %conv2, %conv
- %add.off = add i64 %add, 2147483648
-; CHECK: llvm.sadd.with.overflow
- %0 = icmp ugt i64 %add.off, 4294967295
- br i1 %0, label %if.then, label %if.end
-
-if.then:
- %call = tail call i32 (...)* @throwAnExceptionOrWhatever() nounwind
- br label %if.end
-
-if.end:
-; CHECK-NOT: trunc
- %conv9 = trunc i64 %add to i32
-; CHECK: ret i32
- ret i32 %conv9
-}
-
-declare i32 @throwAnExceptionOrWhatever(...)
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