[llvm] [X86] Refine X86::isOffsetSuitableForCodeModel() (PR #75641)
Arthur Eubanks via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 15 10:43:36 PST 2023
https://github.com/aeubanks created https://github.com/llvm/llvm-project/pull/75641
By treating the medium code model the same as the small code model for small data.
The small code model with large data is already broken (should be 64 bit
constants) so those changes don't matter.
>From 318bd6d6c9e1d55692f48f97d7953ebc3a5d746c Mon Sep 17 00:00:00 2001
From: Arthur Eubanks <aeubanks at google.com>
Date: Fri, 8 Dec 2023 11:20:22 -0800
Subject: [PATCH] [X86] Refine X86::isOffsetSuitableForCodeModel()
By treating the medium code model the same as the small code model for small data.
The small code model with large data is already broken (should be 64 bit
constants) so those changes don't matter.
---
llvm/lib/Target/X86/X86ISelDAGToDAG.cpp | 6 ++--
llvm/lib/Target/X86/X86ISelLowering.cpp | 38 +++++++++++++------------
llvm/lib/Target/X86/X86ISelLowering.h | 7 +++--
llvm/test/CodeGen/X86/code-model-elf.ll | 19 ++++++-------
4 files changed, 36 insertions(+), 34 deletions(-)
diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 7ec59c74f5f58c..61c606a3433cfc 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1736,11 +1736,9 @@ bool X86DAGToDAGISel::foldOffsetIntoAddress(uint64_t Offset,
if (Val != 0 && (AM.ES || AM.MCSym))
return true;
- CodeModel::Model M = TM.getCodeModel();
if (Subtarget->is64Bit()) {
- if (Val != 0 &&
- !X86::isOffsetSuitableForCodeModel(Val, M,
- AM.hasSymbolicDisplacement()))
+ if (Val != 0 && !X86::isOffsetSuitableForCodeModel(
+ Val, TM, AM.GV, AM.hasSymbolicDisplacement()))
return true;
// In addition to the checks required for a register base, check that
// we do not try to use an unsafe Disp with a frame index.
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index cb117475dbe4cf..83ecbb15549566 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -2674,34 +2674,35 @@ SDValue X86TargetLowering::getReturnAddressFrameIndex(SelectionDAG &DAG) const {
return DAG.getFrameIndex(ReturnAddrIndex, getPointerTy(DAG.getDataLayout()));
}
-bool X86::isOffsetSuitableForCodeModel(int64_t Offset, CodeModel::Model M,
- bool hasSymbolicDisplacement) {
+bool X86::isOffsetSuitableForCodeModel(int64_t Offset, const TargetMachine &TM,
+ const GlobalValue *GV,
+ bool HasSymbolicDisplacement) {
// Offset should fit into 32 bit immediate field.
if (!isInt<32>(Offset))
return false;
// If we don't have a symbolic displacement - we don't have any extra
// restrictions.
- if (!hasSymbolicDisplacement)
+ if (!HasSymbolicDisplacement)
return true;
- // FIXME: Some tweaks might be needed for medium code model.
- if (M != CodeModel::Small && M != CodeModel::Kernel)
+ // We can fold offsets in cases where we have a 64-bit relocation, but it
+ // doesn't really help.
+ if (TM.getCodeModel() == CodeModel::Large ||
+ (GV && TM.isLargeGlobalValue(GV)))
return false;
- // For small code model we assume that latest object is 16MB before end of 31
- // bits boundary. We may also accept pretty large negative constants knowing
- // that all objects are in the positive half of address space.
- if (M == CodeModel::Small && Offset < 16*1024*1024)
- return true;
-
// For kernel code model we know that all object resist in the negative half
// of 32bits address space. We may not accept negative offsets, since they may
// be just off and we may accept pretty large positive ones.
- if (M == CodeModel::Kernel && Offset >= 0)
- return true;
+ if (TM.getCodeModel() == CodeModel::Kernel)
+ return Offset >= 0;
- return false;
+ // For other non-large code models we assume that latest small object is 16MB
+ // before end of 31 bits boundary. We may also accept pretty large negative
+ // constants knowing that all objects are in the positive half of address
+ // space.
+ return Offset < 16 * 1024 * 1024;
}
/// Return true if the condition is an signed comparison operation.
@@ -18449,7 +18450,6 @@ SDValue X86TargetLowering::LowerGlobalOrExternal(SDValue Op, SelectionDAG &DAG,
bool HasPICReg = isGlobalRelativeToPICBase(OpFlags);
bool NeedsLoad = isGlobalStubReference(OpFlags);
- CodeModel::Model M = DAG.getTarget().getCodeModel();
auto PtrVT = getPointerTy(DAG.getDataLayout());
SDValue Result;
@@ -18461,7 +18461,8 @@ SDValue X86TargetLowering::LowerGlobalOrExternal(SDValue Op, SelectionDAG &DAG,
// relocation will compute to a negative value, which is invalid.
int64_t GlobalOffset = 0;
if (OpFlags == X86II::MO_NO_FLAG && Offset >= 0 &&
- X86::isOffsetSuitableForCodeModel(Offset, M, true)) {
+ X86::isOffsetSuitableForCodeModel(Offset, getTargetMachine(), GV,
+ true)) {
std::swap(GlobalOffset, Offset);
}
Result = DAG.getTargetGlobalAddress(GV, dl, PtrVT, GlobalOffset, OpFlags);
@@ -33525,8 +33526,9 @@ bool X86TargetLowering::isLegalAddressingMode(const DataLayout &DL,
CodeModel::Model M = getTargetMachine().getCodeModel();
// X86 allows a sign-extended 32-bit immediate field as a displacement.
- if (!X86::isOffsetSuitableForCodeModel(AM.BaseOffs, M, AM.BaseGV != nullptr))
- return false;
+ if (!X86::isOffsetSuitableForCodeModel(AM.BaseOffs, getTargetMachine(),
+ AM.BaseGV, AM.BaseGV != nullptr))
+ return false;
if (AM.BaseGV) {
unsigned GVFlags = Subtarget.classifyGlobalReference(AM.BaseGV);
diff --git a/llvm/lib/Target/X86/X86ISelLowering.h b/llvm/lib/Target/X86/X86ISelLowering.h
index 9bd1622cb0d3a6..5d3a16792046ea 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.h
+++ b/llvm/lib/Target/X86/X86ISelLowering.h
@@ -933,8 +933,11 @@ namespace llvm {
/// Returns true of the given offset can be
/// fit into displacement field of the instruction.
- bool isOffsetSuitableForCodeModel(int64_t Offset, CodeModel::Model M,
- bool hasSymbolicDisplacement);
+ /// GV can be null if not referencing a GlobalValue (e.g. constant pool,
+ /// jump table, etc.).
+ bool isOffsetSuitableForCodeModel(int64_t Offset, const TargetMachine &TM,
+ const GlobalValue *GV,
+ bool HasSymbolicDisplacement);
/// Determines whether the callee is required to pop its
/// own arguments. Callee pop is necessary to support tail calls.
diff --git a/llvm/test/CodeGen/X86/code-model-elf.ll b/llvm/test/CodeGen/X86/code-model-elf.ll
index be93f6530ae4c4..d44363e24783bd 100644
--- a/llvm/test/CodeGen/X86/code-model-elf.ll
+++ b/llvm/test/CodeGen/X86/code-model-elf.ll
@@ -385,8 +385,8 @@ define dso_local i32 @load_forced_small_data() #0 {
;
; MEDIUM-STATIC-LABEL: load_forced_small_data:
; MEDIUM-STATIC: # %bb.0:
-; MEDIUM-STATIC-NEXT: movl $forced_small_data, %eax
-; MEDIUM-STATIC-NEXT: movl 8(%rax), %eax
+; MEDIUM-STATIC-NEXT: movl $forced_small_data+8, %eax
+; MEDIUM-STATIC-NEXT: movl (%rax), %eax
; MEDIUM-STATIC-NEXT: retq
;
; LARGE-STATIC-LABEL: load_forced_small_data:
@@ -402,14 +402,12 @@ define dso_local i32 @load_forced_small_data() #0 {
;
; MEDIUM-SMALL-DATA-PIC-LABEL: load_forced_small_data:
; MEDIUM-SMALL-DATA-PIC: # %bb.0:
-; MEDIUM-SMALL-DATA-PIC-NEXT: leaq forced_small_data(%rip), %rax
-; MEDIUM-SMALL-DATA-PIC-NEXT: movl 8(%rax), %eax
+; MEDIUM-SMALL-DATA-PIC-NEXT: movl forced_small_data+8(%rip), %eax
; MEDIUM-SMALL-DATA-PIC-NEXT: retq
;
; MEDIUM-PIC-LABEL: load_forced_small_data:
; MEDIUM-PIC: # %bb.0:
-; MEDIUM-PIC-NEXT: leaq forced_small_data(%rip), %rax
-; MEDIUM-PIC-NEXT: movl 8(%rax), %eax
+; MEDIUM-PIC-NEXT: movl forced_small_data+8(%rip), %eax
; MEDIUM-PIC-NEXT: retq
;
; LARGE-PIC-LABEL: load_forced_small_data:
@@ -497,7 +495,8 @@ define dso_local ptr @lea_forced_large_data() #0 {
define dso_local i32 @load_forced_large_data() #0 {
; SMALL-STATIC-LABEL: load_forced_large_data:
; SMALL-STATIC: # %bb.0:
-; SMALL-STATIC-NEXT: movl forced_large_data+8(%rip), %eax
+; SMALL-STATIC-NEXT: movl $8, %eax
+; SMALL-STATIC-NEXT: movl forced_large_data(%rax), %eax
; SMALL-STATIC-NEXT: retq
;
; MEDIUM-STATIC-LABEL: load_forced_large_data:
@@ -515,7 +514,8 @@ define dso_local i32 @load_forced_large_data() #0 {
; SMALL-PIC-LABEL: load_forced_large_data:
; SMALL-PIC: # %bb.0:
; SMALL-PIC-NEXT: leaq _GLOBAL_OFFSET_TABLE_(%rip), %rax
-; SMALL-PIC-NEXT: movl forced_large_data at GOTOFF+8(%rax), %eax
+; SMALL-PIC-NEXT: movl $8, %ecx
+; SMALL-PIC-NEXT: movl forced_large_data at GOTOFF(%rax,%rcx), %eax
; SMALL-PIC-NEXT: retq
;
; MEDIUM-SMALL-DATA-PIC-LABEL: load_forced_large_data:
@@ -580,8 +580,7 @@ define dso_local i32 @load_global_data() #0 {
;
; MEDIUM-SMALL-DATA-PIC-LABEL: load_global_data:
; MEDIUM-SMALL-DATA-PIC: # %bb.0:
-; MEDIUM-SMALL-DATA-PIC-NEXT: leaq global_data(%rip), %rax
-; MEDIUM-SMALL-DATA-PIC-NEXT: movl 8(%rax), %eax
+; MEDIUM-SMALL-DATA-PIC-NEXT: movl global_data+8(%rip), %eax
; MEDIUM-SMALL-DATA-PIC-NEXT: retq
;
; MEDIUM-PIC-LABEL: load_global_data:
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