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[ARM] Don't shrink STM if it would cause an unknown base register store 

If a 16-bit thumb STM with writeback stores the base register but it isn't the
first register in the list, then an unknown value is stored. The load/store
optimizer knows this and generates a 32-bit STM without writeback instead, but
thumb2 size reduction converts it into a 16-bit STM. Fix this by having thumb2
size reduction notice such STMs and leave them as they are.

Differential Revision: https://reviews.llvm.org/D78493
This commit is contained in:
John Brawn 2020-04-22 12:07:15 +01:00 committed by John Brawn
parent 41d52662d5
commit 8211cfb7c8
2 changed files with 89 additions and 17 deletions
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16
llvm/lib/Target/ARM/Thumb2SizeReduction.cpp
View File

@ -516,13 +516,23 @@ Thumb2SizeReduce::ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
isLdStMul = true; isLdStMul = true;
break; break;
} }
case ARM::t2STMIA: case ARM::t2STMIA: {
// If the base register is killed, we don't care what its value is after the // t2STMIA is reduced to tSTMIA_UPD which has writeback. We can only do this
// instruction, so we can use an updating STMIA. // if the base register is killed, as then it doesn't matter what its value
// is after the instruction.
if (!MI->getOperand(0).isKill()) if (!MI->getOperand(0).isKill())
return false; return false;
// If the base register is in the register list and isn't the lowest
// numbered register (i.e. it's in operand 4 onwards) then with writeback
// the stored value is unknown, so we can't convert to tSTMIA_UPD.
Register BaseReg = MI->getOperand(0).getReg();
for (unsigned i = 4; i < MI->getNumOperands(); ++i)
if (MI->getOperand(i).getReg() == BaseReg)
return false;
break; break;
}
case ARM::t2LDMIA_RET: { case ARM::t2LDMIA_RET: {
Register BaseReg = MI->getOperand(1).getReg(); Register BaseReg = MI->getOperand(1).getReg();
if (BaseReg != ARM::SP) if (BaseReg != ARM::SP)

90
llvm/test/CodeGen/Thumb/stm-deprecated.ll
View File

@ -1,19 +1,81 @@
; RUN: llc -mtriple=thumbv6m-eabi -verify-machineinstrs %s -o - | FileCheck %s ; RUN: llc -mtriple=thumbv6m-eabi -verify-machineinstrs %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-T1
; RUN: llc -mtriple=thumbv5e-linux-gnueabi -verify-machineinstrs %s -o - | FileCheck %s ; RUN: llc -mtriple=thumbv5e-linux-gnueabi -verify-machineinstrs %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-T1
; RUN: llc -mtriple=thumbv7m -verify-machineinstrs %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-T2
; RUN: llc -mtriple=thumbv7a -verify-machineinstrs %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-T2
%0 = type { %0*, %0*, i32 } %struct1 = type { %struct1*, %struct1*, i32 }
%struct2 = type { i32, i32, i32* }
@x1 = external global %0, align 4 @x1 = external global %struct1, align 4
@x2 = external global %0, align 4 @x2 = external global %struct1, align 4
; CHECK: str r0, [r1] declare void @fn1(i32, i32)
; CHECK-NEXT: str r1, [r1, #4] declare void @fn2(%struct2*)
; CHECK-LABEL: test1:
; CHECK-T1: str r0, [r1]
; CHECK-T1-NEXT: str r1, [r1, #4]
; CHECK-T2: strd r0, r1, [r1]
; CHECK-NOT: stm ; CHECK-NOT: stm
define void @test1(i32 %unused, %struct1* %x) {
define void @foo(i32 %unused, %0* %x) { %first = getelementptr inbounds %struct1, %struct1* %x, i32 0, i32 0
%first = getelementptr inbounds %0, %0* %x, i32 0, i32 0 %second = getelementptr inbounds %struct1, %struct1* %x, i32 0, i32 1
%second = getelementptr inbounds %0, %0* %x, i32 0, i32 1 store %struct1* @x1, %struct1** %first
store %0* @x1, %0** %first store %struct1* %x, %struct1** %second
store %0* %x, %0** %second ret void
unreachable }
; CHECK-LABEL: test2:
; CHECK-T1: str r0, [r2]
; CHECK-T1-NEXT: str r1, [r2, #4]
; CHECK-T1-NEXT: str r2, [r2, #8]
; CHECK-T2: stm.w r2, {r0, r1, r2}
; CHECK-NOT: stm r2!, {r0, r1, r2}
define i32 @test2(i32 %a, i32 %b, %struct2* %p) {
entry:
%p1 = getelementptr inbounds %struct2, %struct2* %p, i32 0, i32 0
%p2 = getelementptr inbounds %struct2, %struct2* %p, i32 0, i32 1
%p3 = getelementptr inbounds %struct2, %struct2* %p, i32 0, i32 2
store i32 %a, i32* %p1, align 4
store i32 %b, i32* %p2, align 4
store i32* %p1, i32** %p3, align 4
call void @fn1(i32 %a, i32 %b)
ret i32 0
}
; CHECK-LABEL: test3:
; CHECK-T1: str r0, [r2]
; CHECK-T1-NEXT: str r1, [r2, #4]
; CHECK-T1-NEXT: str r2, [r2, #8]
; CHECK-T2: stm.w r2, {r0, r1, r2}
; CHECK-NOT: stm r2!, {r0, r1, r2}
define i32 @test3(i32 %a, i32 %b, %struct2* %p) {
entry:
%p1 = getelementptr inbounds %struct2, %struct2* %p, i32 0, i32 0
%p2 = getelementptr inbounds %struct2, %struct2* %p, i32 0, i32 1
%p3 = getelementptr inbounds %struct2, %struct2* %p, i32 0, i32 2
store i32 %a, i32* %p1, align 4
store i32 %b, i32* %p2, align 4
store i32* %p1, i32** %p3, align 4
%p4 = getelementptr inbounds %struct2, %struct2* %p, i32 1
call void @fn2(%struct2* %p4)
ret i32 0
}
; FIXME: We should be using stm in both thumb1 and thumb2
; CHECK-LABEL: test4:
; CHECK-T1: str r0, [r0]
; CHECK-T1-NEXT: str r1, [r0, #4]
; CHECK-T1-NEXT: str r2, [r0, #8]
; CHECK-T2: stm r0!, {r0, r1, r2}
define i32 @test4(%struct1* %p, %struct1* %q, i32 %a) {
entry:
%p1 = getelementptr inbounds %struct1, %struct1* %p, i32 0, i32 0
%p2 = getelementptr inbounds %struct1, %struct1* %p, i32 0, i32 1
%p3 = getelementptr inbounds %struct1, %struct1* %p, i32 0, i32 2
store %struct1* %p, %struct1** %p1, align 4
store %struct1* %q, %struct1** %p2, align 4
store i32 %a, i32* %p3, align 4
call void @fn1(i32 %a, i32 %a)
ret i32 0
} }