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[X86] Disabling PLT in Regcall CC Functions

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According to psABI, PLT stub clobbers XMM8-XMM15.
In Regcall calling convention those registers are used for passing parameters. 
Thus we need to prevent lazy binding in Regcall.

Differential Revision: https://reviews.llvm.org/D32430

llvm-svn: 302124
This commit is contained in:
Oren Ben Simhon 2017-05-04 07:22:49 +00:00
parent 06092c7546
commit 3bc4b0f88f
2 changed files with 52 additions and 2 deletions
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10
lib/Target/X86/X86Subtarget.cpp
View File

@ -139,12 +139,18 @@ X86Subtarget::classifyGlobalFunctionReference(const GlobalValue *GV,
return X86II::MO_NO_FLAG;
assert(!isTargetCOFF());
const Function *F = dyn_cast_or_null<Function>(GV);
if (isTargetELF())
if (isTargetELF()) {
if (is64Bit() && F && (CallingConv::X86_RegCall == F->getCallingConv()))
// According to psABI, PLT stub clobbers XMM8-XMM15.
// In Regcall calling convention those registers are used for passing
// parameters. Thus we need to prevent lazy binding in Regcall.
return X86II::MO_GOTPCREL;
return X86II::MO_PLT;
}
if (is64Bit()) {
auto *F = dyn_cast_or_null<Function>(GV);
if (F && F->hasFnAttribute(Attribute::NonLazyBind))
// If the function is marked as non-lazy, generate an indirect call
// which loads from the GOT directly. This avoids runtime overhead

44
test/CodeGen/X86/regcall-no-plt.ll Normal file
View File

@ -0,0 +1,44 @@
; RUN: llc -mtriple=x86_64-unknown-linux-gnu -relocation-model=pic < %s | FileCheck %s
; RUN: llc -mtriple=x86_64-freebsd -relocation-model=pic < %s | FileCheck %s
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; According to x86-64 psABI, xmm0-xmm7 can be used to pass function parameters.
;; However regcall calling convention uses also xmm8-xmm15 to pass function
;; parameters which violates x86-64 psABI.
;; Detail info about it can be found at:
;; https://sourceware.org/bugzilla/show_bug.cgi?id=21265
;;
;; We encounter the violation symptom when using PIC with lazy binding
;; optimization.
;; In that case the PLT mechanism as described in x86_64 psABI will
;; not preserve xmm8-xmm15 registers and will lead to miscompilation.
;;
;; The agreed solution is to disable PLT for regcall calling convention for
;; SystemV using ELF format.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
declare void @lazy()
declare x86_regcallcc void @regcall_not_lazy()
; CHECK-LABEL: foo:
; CHECK: callq lazy@PLT
; CHECK: callq *regcall_not_lazy@GOTPCREL(%rip)
define void @foo() nounwind {
call void @lazy()
call void @regcall_not_lazy()
ret void
}
; CHECK-LABEL: tail_call_regcall:
; CHECK: jmpq *regcall_not_lazy@GOTPCREL(%rip)
define void @tail_call_regcall() nounwind {
tail call void @regcall_not_lazy()
ret void
}
; CHECK-LABEL: tail_call_regular:
; CHECK: jmp lazy
define void @tail_call_regular() nounwind {
tail call void @lazy()
ret void
}