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llvm-mirror/test/CodeGen/Mips/eh-dwarf-cfa.ll
Simon Dardis 1f6e565a78 [mips] Optimize stack pointer adjustments.
Instead of always using addu to adjust the stack pointer when the
size out is of the range of an addiu instruction, use subu so that
a smaller constant can be generated.

This can give savings of ~3 instructions whenever a function has a
a stack frame whose size is out of range of an addiu instruction.

This change may break some naive stack unwinders.

Partially resolves PR/26291.

Thanks to David Chisnall for reporting the issue.

Reviewers: dsanders, vkalintiris

Differential Review: http://reviews.llvm.org/D21321

llvm-svn: 272666
2016-06-14 13:39:43 +00:00

74 lines
1.7 KiB
LLVM

; RUN: llc -march=mipsel -mcpu=mips32 < %s | FileCheck %s
; RUN: llc -march=mips64el -mcpu=mips4 < %s | \
; RUN: FileCheck %s -check-prefix=CHECK-MIPS64
; RUN: llc -march=mips64el -mcpu=mips64 < %s | \
; RUN: FileCheck %s -check-prefix=CHECK-MIPS64
declare i8* @llvm.eh.dwarf.cfa(i32) nounwind
declare i8* @llvm.frameaddress(i32) nounwind readnone
define i8* @f1() nounwind {
entry:
%x = alloca [32 x i8], align 1
%0 = call i8* @llvm.eh.dwarf.cfa(i32 0)
ret i8* %0
; CHECK-LABEL: f1:
; CHECK: addiu $sp, $sp, -32
; CHECK: addiu $2, $sp, 32
}
define i8* @f2() nounwind {
entry:
%x = alloca [65536 x i8], align 1
%0 = call i8* @llvm.eh.dwarf.cfa(i32 0)
ret i8* %0
; CHECK-LABEL: f2:
; check stack size (65536 + 8)
; CHECK: lui $[[R0:[a-z0-9]+]], 1
; CHECK: addiu $[[R0]], $[[R0]], 8
; CHECK: subu $sp, $sp, $[[R0]]
; check return value ($sp + stack size)
; CHECK: lui $[[R1:[a-z0-9]+]], 1
; CHECK: addu $[[R1]], $sp, $[[R1]]
; CHECK: addiu $2, $[[R1]], 8
}
define i32 @f3() nounwind {
entry:
%x = alloca [32 x i8], align 1
%0 = call i8* @llvm.eh.dwarf.cfa(i32 0)
%1 = ptrtoint i8* %0 to i32
%2 = call i8* @llvm.frameaddress(i32 0)
%3 = ptrtoint i8* %2 to i32
%add = add i32 %1, %3
ret i32 %add
; CHECK-LABEL: f3:
; CHECK: addiu $sp, $sp, -40
; check return value ($fp + stack size + $fp)
; CHECK: addiu $[[R0:[a-z0-9]+]], $fp, 40
; CHECK: addu $2, $[[R0]], $fp
}
define i8* @f4() nounwind {
entry:
%x = alloca [32 x i8], align 1
%0 = call i8* @llvm.eh.dwarf.cfa(i32 0)
ret i8* %0
; CHECK-LABEL: f4:
; CHECK-MIPS64: daddiu $sp, $sp, -32
; CHECK-MIPS64: daddiu $2, $sp, 32
}