[CodeGenPrepare] Don't create dead instructions in addrmode sinking

When we fail to sink an instruction, we must make sure not to modify
the function; otherwise, we end up in an infinite loop because
CodeGenPrepare iterates until it doesn't make any changes.

Fixes https://bugs.llvm.org/show_bug.cgi?id=33608 .

llvm-svn: 307866
This commit is contained in:
Eli Friedman 2017-07-12 23:30:02 +00:00
parent c1e903be19
commit 6f7c9ad7d4
2 changed files with 42 additions and 12 deletions

View File

@ -4393,6 +4393,20 @@ bool CodeGenPrepare::optimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
AddrMode.Scale = 0;
}
// It is only safe to sign extend the BaseReg if we know that the math
// required to create it did not overflow before we extend it. Since
// the original IR value was tossed in favor of a constant back when
// the AddrMode was created we need to bail out gracefully if widths
// do not match instead of extending it.
//
// (See below for code to add the scale.)
if (AddrMode.Scale) {
Type *ScaledRegTy = AddrMode.ScaledReg->getType();
if (cast<IntegerType>(IntPtrTy)->getBitWidth() >
cast<IntegerType>(ScaledRegTy)->getBitWidth())
return false;
}
if (AddrMode.BaseGV) {
if (ResultPtr)
return false;
@ -4443,19 +4457,11 @@ bool CodeGenPrepare::optimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
Value *V = AddrMode.ScaledReg;
if (V->getType() == IntPtrTy) {
// done.
} else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
cast<IntegerType>(V->getType())->getBitWidth()) {
V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
} else {
// It is only safe to sign extend the BaseReg if we know that the math
// required to create it did not overflow before we extend it. Since
// the original IR value was tossed in favor of a constant back when
// the AddrMode was created we need to bail out gracefully if widths
// do not match instead of extending it.
Instruction *I = dyn_cast_or_null<Instruction>(ResultIndex);
if (I && (ResultIndex != AddrMode.BaseReg))
I->eraseFromParent();
return false;
assert(cast<IntegerType>(IntPtrTy)->getBitWidth() <
cast<IntegerType>(V->getType())->getBitWidth() &&
"We can't transform if ScaledReg is too narrow");
V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
}
if (AddrMode.Scale != 1)

View File

@ -4,6 +4,8 @@ target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"
@x = external global [1 x [2 x <4 x float>]]
; Can we sink single addressing mode computation to use?
define void @test1(i1 %cond, i64* %base) {
; CHECK-LABEL: @test1
@ -194,3 +196,25 @@ rare.2:
declare void @slowpath(i32, i32*)
; Make sure we don't end up in an infinite loop after we fail to sink.
; CHECK-LABEL: define void @test8
; CHECK: %ptr = getelementptr i8, i8* %aFOO_load_ptr2int_2void, i32 undef
define void @test8() {
allocas:
%aFOO_load = load float*, float** undef
%aFOO_load_ptr2int = ptrtoint float* %aFOO_load to i64
%aFOO_load_ptr2int_broadcast_init = insertelement <4 x i64> undef, i64 %aFOO_load_ptr2int, i32 0
%aFOO_load_ptr2int_2void = inttoptr i64 %aFOO_load_ptr2int to i8*
%ptr = getelementptr i8, i8* %aFOO_load_ptr2int_2void, i32 undef
br label %load.i145
load.i145:
%ptr.i143 = bitcast i8* %ptr to <4 x float>*
%valall.i144 = load <4 x float>, <4 x float>* %ptr.i143, align 4
%x_offset = getelementptr [1 x [2 x <4 x float>]], [1 x [2 x <4 x float>]]* @x, i32 0, i64 0
br label %pl_loop.i.i122
pl_loop.i.i122:
br label %pl_loop.i.i122
}