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[AlignmentFromAssumptions] Fix a SCEV assertion resulting from address space differences.

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Summary:
On targets with different pointer sizes, -alignment-from-assumptions could attempt to create SCEV expressions which use different effective SCEV types. The provided test illustrates the issue.

In `getNewAlignment`, AASCEV would be the (only) alloca, which would have an effective SCEV type of i32. But PtrSCEV, the GEP in this case, due to being in the flat/default address space, will have an effective SCEV of i64.

This patch resolves the issue by truncating PtrSCEV to AASCEV's effective type.

Reviewers: hfinkel, jdoerfert

Reviewed By: jdoerfert

Subscribers: jvesely, nhaehnle, hiraditya, javed.absar, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75471
This commit is contained in:
Richard Diamond 2020-03-02 12:08:57 -06:00
parent 115066186a
commit 527a4d99f8
2 changed files with 38 additions and 0 deletions
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5
lib/Transforms/Scalar/AlignmentFromAssumptions.cpp
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@ -127,6 +127,11 @@ static unsigned getNewAlignment(const SCEV *AASCEV, const SCEV *AlignSCEV,
const SCEV *OffSCEV, Value *Ptr,
ScalarEvolution *SE) {
const SCEV *PtrSCEV = SE->getSCEV(Ptr);
// On a platform with 32-bit allocas, but 64-bit flat/global pointer sizes
// (*cough* AMDGPU), the effective SCEV type of AASCEV and PtrSCEV
// may disagree. Trunc/extend so they agree.
PtrSCEV = SE->getTruncateOrZeroExtend(
PtrSCEV, SE->getEffectiveSCEVType(AASCEV->getType()));
const SCEV *DiffSCEV = SE->getMinusSCEV(PtrSCEV, AASCEV);
// On 32-bit platforms, DiffSCEV might now have type i32 -- we've always

33
test/Transforms/AlignmentFromAssumptions/amdgpu-crash.ll Normal file
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@ -0,0 +1,33 @@
; Test that we don't crash.
; RUN: opt < %s -alignment-from-assumptions -S
; RUN: opt < %s -passes=alignment-from-assumptions -S
target datalayout = "e-p:64:64-p1:64:64-p2:32:32-p3:32:32-p4:64:64-p5:32:32-p6:32:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S32-A5-ni:7"
%"core::str::CharIndices.29.66.90.114.138.149.165.173.181.197.205.213.229.387.398" = type { [0 x i64], i64, [0 x i64], { i8*, i8* }, [0 x i64] }
%"unwind::libunwind::_Unwind_Exception.9.51.75.99.123.147.163.171.179.195.203.211.227.385.396" = type { [0 x i64], i64, [0 x i64], void (i32, %"unwind::libunwind::_Unwind_Exception.9.51.75.99.123.147.163.171.179.195.203.211.227.385.396"*)*, [0 x i64], [6 x i64], [0 x i64] }
%"unwind::libunwind::_Unwind_Context.10.52.76.100.124.148.164.172.180.196.204.212.228.386.397" = type { [0 x i8] }
define void @"_ZN44_$LT$$RF$T$u20$as$u20$core..fmt..Display$GT$3fmt17h7b1d039c7ff5e1feE"() {
start:
%_15.i.i = alloca %"core::str::CharIndices.29.66.90.114.138.149.165.173.181.197.205.213.229.387.398", align 8, addrspace(5)
br label %bb12.i.i
bb12.i.i: ; preds = %start
%0 = addrspacecast %"core::str::CharIndices.29.66.90.114.138.149.165.173.181.197.205.213.229.387.398" addrspace(5)* %_15.i.i to %"core::str::CharIndices.29.66.90.114.138.149.165.173.181.197.205.213.229.387.398"*
%ptrint53.i.i = ptrtoint %"core::str::CharIndices.29.66.90.114.138.149.165.173.181.197.205.213.229.387.398"* %0 to i64
%maskedptr54.i.i = and i64 %ptrint53.i.i, 7
%maskcond55.i.i = icmp eq i64 %maskedptr54.i.i, 0
call void @llvm.assume(i1 %maskcond55.i.i)
br i1 undef, label %bb20.i.i, label %bb3.i.i.i.i.i.preheader.i.i
bb3.i.i.i.i.i.preheader.i.i: ; preds = %bb12.i.i
%1 = getelementptr inbounds %"core::str::CharIndices.29.66.90.114.138.149.165.173.181.197.205.213.229.387.398", %"core::str::CharIndices.29.66.90.114.138.149.165.173.181.197.205.213.229.387.398"* %0, i64 0, i32 0, i64 0
store i64 0, i64* %1, align 8
unreachable
bb20.i.i: ; preds = %bb12.i.i
ret void
}
declare void @llvm.assume(i1)