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9c5cfee3f9
Summary: Use this code pattern when RAX is live, instead of emitting up to 2 billion adjustments: pushq %rax movabsq +-$Offset+-8, %rax addq %rsp, %rax xchg %rax, (%rsp) movq (%rsp), %rsp Try to clean this code up a bit while I'm here. In particular, hoist the logic that handles the entire adjustment with `movabsq $imm, %rax` out of the loop. This negates the offset in the prologue and uses ADD because X86 only has a two operand subtract which always subtracts from the destination register, which can no longer be RSP. Fixes PR31962 Reviewers: majnemer, sdardis Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D30052 llvm-svn: 298116
63 lines
2.2 KiB
LLVM
63 lines
2.2 KiB
LLVM
; RUN: llc < %s -mtriple=x86_64-linux | FileCheck %s --check-prefix=CHECK
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; Test how we handle pathologically large stack frames when RAX is live through
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; the prologue and epilogue.
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declare void @bar(i8*)
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declare void @llvm.va_start(i8*)
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; For stack frames between 2GB and 16GB, do multiple adjustments.
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define i32 @stack_frame_8gb(i32 %x, ...) nounwind {
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; CHECK-LABEL: stack_frame_8gb:
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; CHECK: subq ${{.*}}, %rsp # imm = 0x7FFFFFFF
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; CHECK: subq ${{.*}}, %rsp # imm = 0x7FFFFFFF
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; CHECK: subq ${{.*}}, %rsp # imm = 0x7FFFFFFF
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; CHECK: subq ${{.*}}, %rsp # imm = 0x7FFFFFFF
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; CHECK: subq ${{.*}}, %rsp
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; CHECK: callq bar
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; CHECK: addq ${{.*}}, %rsp # imm = 0x7FFFFFFF
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; CHECK: addq ${{.*}}, %rsp # imm = 0x7FFFFFFF
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; CHECK: addq ${{.*}}, %rsp # imm = 0x7FFFFFFF
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; CHECK: addq ${{.*}}, %rsp # imm = 0x7FFFFFFF
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; CHECK: addq ${{.*}}, %rsp
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; CHECK: retq
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%1 = alloca [u0x200000000 x i8]
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%va = alloca i8, i32 24
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call void @llvm.va_start(i8* %va)
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%2 = getelementptr inbounds [u0x200000000 x i8], [u0x200000000 x i8]* %1, i32 0, i32 0
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call void @bar(i8* %2)
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ret i32 %x
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}
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; For stack frames larger than 16GB, spill EAX instead of doing a linear number
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; of adjustments.
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; This function should have a frame size of 0x4000000D0. The 0xD0 is 208 bytes
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; from 24 bytes of va_list, 176 bytes of spilled varargs regparms, and 8 bytes
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; of alignment. We subtract 8 less and add 8 more in the prologue and epilogue
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; respectively to account for the PUSH.
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define i32 @stack_frame_16gb(i32 %x, ...) nounwind {
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; CHECK-LABEL: stack_frame_16gb:
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; CHECK: pushq %rax
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; CHECK-NEXT: movabsq ${{.*}}, %rax # imm = 0xFFFFFFFBFFFFFF38
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; CHECK-NEXT: addq %rsp, %rax
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; CHECK-NEXT: xchgq %rax, (%rsp)
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; CHECK-NEXT: movq (%rsp), %rsp
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; CHECK: callq bar
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; CHECK: pushq %rax
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; CHECK-NEXT: movabsq ${{.*}}, %rax # imm = 0x4000000D8
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; CHECK-NEXT: addq %rsp, %rax
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; CHECK-NEXT: xchgq %rax, (%rsp)
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; CHECK-NEXT: movq (%rsp), %rsp
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; CHECK: retq
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%1 = alloca [u0x400000000 x i8]
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%va = alloca i8, i32 24
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call void @llvm.va_start(i8* %va)
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%2 = getelementptr inbounds [u0x400000000 x i8], [u0x400000000 x i8]* %1, i32 0, i32 0
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call void @bar(i8* %2)
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ret i32 %x
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}
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