[llvm] r268662 - ARM: don't attempt to merge litpools referencing different PC-anchors.
Tim Northover via llvm-commits
llvm-commits at lists.llvm.org
Thu May 5 11:38:53 PDT 2016
Author: tnorthover
Date: Thu May 5 13:38:53 2016
New Revision: 268662
URL: http://llvm.org/viewvc/llvm-project?rev=268662&view=rev
Log:
ARM: don't attempt to merge litpools referencing different PC-anchors.
Given something like:
ldr r0, .LCPI0_0 (== pc-rel var)
add r0, pc
ldr r1, .LCPI0_1 (== pc-rel var)
add r1, pc
we cannot combine the 2 ldr instructions and litpools because they get added to
a different pc to form the correct address. I think the original logic came
from a time when we fused the LDRpci/PICADD instructions into one
pseudo-instruction so the PC was always immediately at-hand. That's no longer
the case.
Should fix general-dynamic TLS access on Linux, and quite possibly other -fPIC
code that relies on litpools (e.g. v6m and -Oz compilations) though trivial
tweaks of the .ll test didn't provoke anything.
Added:
llvm/trunk/test/CodeGen/ARM/litpool-licm.ll
Modified:
llvm/trunk/lib/Target/ARM/ARMConstantPoolValue.cpp
Modified: llvm/trunk/lib/Target/ARM/ARMConstantPoolValue.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMConstantPoolValue.cpp?rev=268662&r1=268661&r2=268662&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMConstantPoolValue.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMConstantPoolValue.cpp Thu May 5 13:38:53 2016
@@ -74,9 +74,9 @@ bool
ARMConstantPoolValue::hasSameValue(ARMConstantPoolValue *ACPV) {
if (ACPV->Kind == Kind &&
ACPV->PCAdjust == PCAdjust &&
- ACPV->Modifier == Modifier) {
- if (ACPV->LabelId == LabelId)
- return true;
+ ACPV->Modifier == Modifier &&
+ ACPV->LabelId == LabelId &&
+ ACPV->AddCurrentAddress == AddCurrentAddress) {
// Two PC relative constpool entries containing the same GV address or
// external symbols. FIXME: What about blockaddress?
if (Kind == ARMCP::CPValue || Kind == ARMCP::CPExtSymbol)
Added: llvm/trunk/test/CodeGen/ARM/litpool-licm.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/litpool-licm.ll?rev=268662&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/litpool-licm.ll (added)
+++ llvm/trunk/test/CodeGen/ARM/litpool-licm.ll Thu May 5 13:38:53 2016
@@ -0,0 +1,46 @@
+; RUN: llc -mtriple=thumbv7-linux-gnueabihf -relocation-model=pic %s -o - | FileCheck %s
+
+ at var = thread_local global i32 0, align 4
+
+define void @func(i32 %n) {
+; CHECK-LABEL: func:
+; CHECK: ldr [[REF1:r[0-9]+]], [[CP1:.LCPI[0-9]+_[0-9]+]]
+; CHECK: ldr [[REF2:r[0-9]+]], [[CP2:.LCPI[0-9]+_[0-9]+]]
+
+; CHECK: [[PCPOS1:.LPC[0-9]+_[0-9]+]]:
+; CHECK-NEXT: add [[REF1]], pc
+
+; CHECK: [[PCPOS2:.LPC[0-9]+_[0-9]+]]:
+; CHECK-NEXT: add [[REF2]], pc
+
+; CHECK: [[CP1]]:
+; CHECK-NEXT: [[CP1_TMP:.Ltmp[0-9]+]]:
+; CHECK-NEXT: .long var(TLSGD)-(([[PCPOS1]]+4)-[[CP1_TMP]])
+
+; CHECK: [[CP2]]:
+; CHECK-NEXT: [[CP2_TMP:.Ltmp[0-9]+]]:
+; CHECK-NEXT: .long var(TLSGD)-(([[PCPOS2]]+4)-[[CP2_TMP]])
+
+entry:
+ br label %loop
+
+loop:
+ %i = phi i32 [ %inc, %next ], [ 0, %entry ]
+ %val = load i32, i32* @var
+ %tst = icmp eq i32 %val, 0
+ br i1 %tst, label %next, label %call
+
+call:
+ tail call void @foo(i32* nonnull @var) #2
+ br label %next
+
+next:
+ %inc = add i32 %i, 1
+ %stop = icmp eq i32 %inc, %n
+ br i1 %stop, label %done, label %loop
+
+done:
+ ret void
+}
+
+declare void @foo(i32*)
\ No newline at end of file
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