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AsmWriter: Write alloca array size explicitly (and -instcombine fixup)

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Write the `alloca` array size explicitly when it's non-canonical.
Previously, if the array size was `iX 1` (where X is not 32), the type
would mutate to `i32` when round-tripping through assembly.

The testcase I added fails in `verify-uselistorder` (as well as
`FileCheck`), since the use-lists for `i32 1` and `i64 1` change.
(Manman Ren came across this when running `verify-uselistorder` on some
non-trivial, optimized code as part of PR5680.)

The type mutation started with r104911, which allowed array sizes to be
something other than an `i32`.  Starting with r204945, we
"canonicalized" to `i64` on 64-bit platforms -- and then on every
round-trip through assembly, mutated back to `i32`.

I bundled a fixup for `-instcombine` to avoid r204945 on scalar
allocations.  (There wasn't a clean way to sequence this into two
commits, since the assembly change on its own caused testcase churn, and
the `-instcombine` change can't be tested without the assembly changes.)

An obvious alternative fix -- change `AllocaInst::AllocaInst()`,
`AsmWriter` and `LLParser` to treat `intptr_t` as the canonical type for
scalar allocations -- was rejected out of hand, since this required
teaching them each about the data layout.

A follow-up commit will add an `-instcombine` to canonicalize the scalar
allocation array size to `i32 1` rather than leaving `iX 1` alone.

rdar://problem/20075773

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232200 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith 2015-03-13 19:30:44 +00:00
parent 7c93bfa994
commit 95ff656ae0
4 changed files with 38 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
lib/IR/AsmWriter.cpp
View File

@ -2885,7 +2885,13 @@ void AssemblyWriter::printInstruction(const Instruction &I) {
if (AI->isUsedWithInAlloca())
Out << "inalloca ";
TypePrinter.print(AI->getAllocatedType(), Out);
if (!AI->getArraySize() || AI->isArrayAllocation()) {
// Explicitly write the array size if the code is broken, if it's an array
// allocation, or if the type is not canonical for scalar allocations. The
// latter case prevents the type from mutating when round-tripping through
// assembly.
if (!AI->getArraySize() || AI->isArrayAllocation() ||
!AI->getArraySize()->getType()->isIntegerTy(32)) {
Out << ", ";
writeOperand(AI->getArraySize(), true);
}

8
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
View File

@ -165,6 +165,10 @@ isOnlyCopiedFromConstantGlobal(AllocaInst *AI,
}
static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
// Check for array size of 1 (scalar allocation).
if (!AI.isArrayAllocation())
return nullptr;
// Ensure that the alloca array size argument has type intptr_t, so that
// any casting is exposed early.
Type *IntPtrTy = IC.getDataLayout().getIntPtrType(AI.getType());
@ -174,10 +178,6 @@ static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
return &AI;
}
// Check C != 1
if (!AI.isArrayAllocation())
return nullptr;
// Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1
if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getZExtValue());

11
test/Assembler/alloca-size-one.ll Normal file
View File

@ -0,0 +1,11 @@
; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
; RUN: verify-uselistorder %s
define void @foo() {
entry:
; CHECK: %alloc32 = alloca i1, align 8
; CHECK: %alloc64 = alloca i1, i64 1, align 8
%alloc32 = alloca i1, i32 1, align 8
%alloc64 = alloca i1, i64 1, align 8
unreachable
}

19
test/Transforms/InstCombine/alloca.ll
View File

@ -1,6 +1,6 @@
; RUN: opt < %s -instcombine -S -default-data-layout="E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s
; RUN: opt < %s -instcombine -S -default-data-layout="E-p:32:32:32-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=P32
; RUN: opt < %s -instcombine -S | FileCheck %s -check-prefix=NODL
; RUN: opt < %s -instcombine -S -default-data-layout="E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=CHECK -check-prefix=ALL
; RUN: opt < %s -instcombine -S -default-data-layout="E-p:32:32:32-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=P32 -check-prefix=ALL
; RUN: opt < %s -instcombine -S | FileCheck %s -check-prefix=NODL -check-prefix=ALL
declare void @use(...)
@ -150,3 +150,16 @@ entry:
call void @llvm.stackrestore(i8* %inalloca.save)
ret void
}
define void @test10() {
entry:
; ALL-LABEL: @test10(
; ALL: %v32 = alloca i1, align 8
; ALL: %v64 = alloca i1, i64 1, align 8
; ALL: %v33 = alloca i1, i33 1, align 8
%v32 = alloca i1, align 8
%v64 = alloca i1, i64 1, align 8
%v33 = alloca i1, i33 1, align 8
call void (...)* @use(i1* %v32, i1* %v64, i1* %v33)
ret void
}