[llvm] [X86] Allow accessing large globals in small code model (PR #74785)
Arthur Eubanks via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 7 15:38:35 PST 2023
https://github.com/aeubanks created https://github.com/llvm/llvm-project/pull/74785
This removes some assumptions that the small code model will only
reference "near" globals.
There are still some missing optimizations and wrong code sequences, but
I'd like to address those separately. This will require auditing any
checks of the code model in the X86 backend.
>From 35f3ac50f8f3d681662c173d3b133a59c8076ab5 Mon Sep 17 00:00:00 2001
From: Arthur Eubanks <aeubanks at google.com>
Date: Thu, 7 Dec 2023 15:35:56 -0800
Subject: [PATCH] [X86] Allow accessing large globals in small code model
This removes some assumptions that the small code model will only
reference "near" globals.
There are still some missing optimizations and wrong code sequences, but
I'd like to address those separately. This will require auditing any
checks of the code model in the X86 backend.
---
llvm/lib/Target/X86/X86InstrInfo.cpp | 31 +--
llvm/test/CodeGen/X86/code-model-elf.ll | 238 +++++++++++++++++++++---
2 files changed, 225 insertions(+), 44 deletions(-)
diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index a69ce40982ad82..d6ae4971d238d8 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -8717,11 +8717,6 @@ bool X86InstrInfo::isSafeToMoveRegClassDefs(
/// TODO: Eliminate this and move the code to X86MachineFunctionInfo.
///
unsigned X86InstrInfo::getGlobalBaseReg(MachineFunction *MF) const {
- assert((!Subtarget.is64Bit() ||
- MF->getTarget().getCodeModel() == CodeModel::Medium ||
- MF->getTarget().getCodeModel() == CodeModel::Large) &&
- "X86-64 PIC uses RIP relative addressing");
-
X86MachineFunctionInfo *X86FI = MF->getInfo<X86MachineFunctionInfo>();
Register GlobalBaseReg = X86FI->getGlobalBaseReg();
if (GlobalBaseReg != 0)
@@ -10083,12 +10078,6 @@ struct CGBR : public MachineFunctionPass {
static_cast<const X86TargetMachine *>(&MF.getTarget());
const X86Subtarget &STI = MF.getSubtarget<X86Subtarget>();
- // Don't do anything in the 64-bit small and kernel code models. They use
- // RIP-relative addressing for everything.
- if (STI.is64Bit() && (TM->getCodeModel() == CodeModel::Small ||
- TM->getCodeModel() == CodeModel::Kernel))
- return false;
-
// Only emit a global base reg in PIC mode.
if (!TM->isPositionIndependent())
return false;
@@ -10114,16 +10103,7 @@ struct CGBR : public MachineFunctionPass {
PC = GlobalBaseReg;
if (STI.is64Bit()) {
- if (TM->getCodeModel() == CodeModel::Medium) {
- // In the medium code model, use a RIP-relative LEA to materialize the
- // GOT.
- BuildMI(FirstMBB, MBBI, DL, TII->get(X86::LEA64r), PC)
- .addReg(X86::RIP)
- .addImm(0)
- .addReg(0)
- .addExternalSymbol("_GLOBAL_OFFSET_TABLE_")
- .addReg(0);
- } else if (TM->getCodeModel() == CodeModel::Large) {
+ if (TM->getCodeModel() == CodeModel::Large) {
// In the large code model, we are aiming for this code, though the
// register allocation may vary:
// leaq .LN$pb(%rip), %rax
@@ -10146,7 +10126,14 @@ struct CGBR : public MachineFunctionPass {
.addReg(PBReg, RegState::Kill)
.addReg(GOTReg, RegState::Kill);
} else {
- llvm_unreachable("unexpected code model");
+ // In other code models, use a RIP-relative LEA to materialize the
+ // GOT.
+ BuildMI(FirstMBB, MBBI, DL, TII->get(X86::LEA64r), PC)
+ .addReg(X86::RIP)
+ .addImm(0)
+ .addReg(0)
+ .addExternalSymbol("_GLOBAL_OFFSET_TABLE_")
+ .addReg(0);
}
} else {
// Operand of MovePCtoStack is completely ignored by asm printer. It's
diff --git a/llvm/test/CodeGen/X86/code-model-elf.ll b/llvm/test/CodeGen/X86/code-model-elf.ll
index 483ffd87ac696f..457c6bde354f2e 100644
--- a/llvm/test/CodeGen/X86/code-model-elf.ll
+++ b/llvm/test/CodeGen/X86/code-model-elf.ll
@@ -41,7 +41,8 @@ target triple = "x86_64--linux"
@extern_data = external global [10 x i32], align 16
@thread_data = external thread_local global i32, align 4
@unknown_size_data = dso_local global [0 x i32] zeroinitializer, align 16
-
+ at forced_small_data = dso_local global [10 x i32] zeroinitializer, code_model "small", align 16
+ at forced_large_data = dso_local global [10 x i32] zeroinitializer, code_model "large", align 16
define dso_local ptr @lea_static_data() #0 {
; SMALL-STATIC-LABEL: lea_static_data:
@@ -223,6 +224,199 @@ define dso_local ptr @lea_unknown_size_data() #0 {
ret ptr @unknown_size_data
}
+; TODO: make nopic small and medium instruction sequence the same
+define dso_local ptr @lea_forced_small_data() #0 {
+; SMALL-STATIC-LABEL: lea_forced_small_data:
+; SMALL-STATIC: # %bb.0:
+; SMALL-STATIC-NEXT: movl $forced_small_data, %eax
+; SMALL-STATIC-NEXT: retq
+;
+; MEDIUM-STATIC-LABEL: lea_forced_small_data:
+; MEDIUM-STATIC: # %bb.0:
+; MEDIUM-STATIC-NEXT: movabsq $forced_small_data, %rax
+; MEDIUM-STATIC-NEXT: retq
+;
+; LARGE-STATIC-LABEL: lea_forced_small_data:
+; LARGE-STATIC: # %bb.0:
+; LARGE-STATIC-NEXT: movabsq $forced_small_data, %rax
+; LARGE-STATIC-NEXT: retq
+;
+; SMALL-PIC-LABEL: lea_forced_small_data:
+; SMALL-PIC: # %bb.0:
+; SMALL-PIC-NEXT: leaq forced_small_data(%rip), %rax
+; SMALL-PIC-NEXT: retq
+;
+; MEDIUM-SMALL-DATA-PIC-LABEL: lea_forced_small_data:
+; MEDIUM-SMALL-DATA-PIC: # %bb.0:
+; MEDIUM-SMALL-DATA-PIC-NEXT: leaq forced_small_data(%rip), %rax
+; MEDIUM-SMALL-DATA-PIC-NEXT: retq
+;
+; MEDIUM-PIC-LABEL: lea_forced_small_data:
+; MEDIUM-PIC: # %bb.0:
+; MEDIUM-PIC-NEXT: leaq forced_small_data(%rip), %rax
+; MEDIUM-PIC-NEXT: retq
+;
+; LARGE-PIC-LABEL: lea_forced_small_data:
+; LARGE-PIC: # %bb.0:
+; LARGE-PIC-NEXT: .L4$pb:
+; LARGE-PIC-NEXT: leaq .L4$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L4$pb, %rcx
+; LARGE-PIC-NEXT: addq %rax, %rcx
+; LARGE-PIC-NEXT: movabsq $forced_small_data at GOTOFF, %rax
+; LARGE-PIC-NEXT: addq %rcx, %rax
+; LARGE-PIC-NEXT: retq
+ ret ptr @forced_small_data
+}
+
+; TODO: make small and medium instruction sequence the same
+define dso_local i32 @load_forced_small_data() #0 {
+; SMALL-STATIC-LABEL: load_forced_small_data:
+; SMALL-STATIC: # %bb.0:
+; SMALL-STATIC-NEXT: movl forced_small_data+8(%rip), %eax
+; SMALL-STATIC-NEXT: retq
+;
+; MEDIUM-STATIC-LABEL: load_forced_small_data:
+; MEDIUM-STATIC: # %bb.0:
+; MEDIUM-STATIC-NEXT: movabsq $forced_small_data, %rax
+; MEDIUM-STATIC-NEXT: movl 8(%rax), %eax
+; MEDIUM-STATIC-NEXT: retq
+;
+; LARGE-STATIC-LABEL: load_forced_small_data:
+; LARGE-STATIC: # %bb.0:
+; LARGE-STATIC-NEXT: movabsq $forced_small_data, %rax
+; LARGE-STATIC-NEXT: movl 8(%rax), %eax
+; LARGE-STATIC-NEXT: retq
+;
+; SMALL-PIC-LABEL: load_forced_small_data:
+; SMALL-PIC: # %bb.0:
+; SMALL-PIC-NEXT: movl forced_small_data+8(%rip), %eax
+; SMALL-PIC-NEXT: retq
+;
+; MEDIUM-SMALL-DATA-PIC-LABEL: load_forced_small_data:
+; MEDIUM-SMALL-DATA-PIC: # %bb.0:
+; MEDIUM-SMALL-DATA-PIC-NEXT: leaq forced_small_data(%rip), %rax
+; MEDIUM-SMALL-DATA-PIC-NEXT: movl 8(%rax), %eax
+; MEDIUM-SMALL-DATA-PIC-NEXT: retq
+;
+; MEDIUM-PIC-LABEL: load_forced_small_data:
+; MEDIUM-PIC: # %bb.0:
+; MEDIUM-PIC-NEXT: leaq forced_small_data(%rip), %rax
+; MEDIUM-PIC-NEXT: movl 8(%rax), %eax
+; MEDIUM-PIC-NEXT: retq
+;
+; LARGE-PIC-LABEL: load_forced_small_data:
+; LARGE-PIC: # %bb.0:
+; LARGE-PIC-NEXT: .L5$pb:
+; LARGE-PIC-NEXT: leaq .L5$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L5$pb, %rcx
+; LARGE-PIC-NEXT: addq %rax, %rcx
+; LARGE-PIC-NEXT: movabsq $forced_small_data at GOTOFF, %rax
+; LARGE-PIC-NEXT: movl 8(%rcx,%rax), %eax
+; LARGE-PIC-NEXT: retq
+ %rv = load i32, ptr getelementptr inbounds (i32, ptr @forced_small_data, i64 2)
+ ret i32 %rv
+}
+
+; TODO: fix small code model instruction sequences to use 64-bit constants
+define dso_local ptr @lea_forced_large_data() #0 {
+; SMALL-STATIC-LABEL: lea_forced_large_data:
+; SMALL-STATIC: # %bb.0:
+; SMALL-STATIC-NEXT: movl $forced_large_data, %eax
+; SMALL-STATIC-NEXT: retq
+;
+; MEDIUM-STATIC-LABEL: lea_forced_large_data:
+; MEDIUM-STATIC: # %bb.0:
+; MEDIUM-STATIC-NEXT: movabsq $forced_large_data, %rax
+; MEDIUM-STATIC-NEXT: retq
+;
+; LARGE-STATIC-LABEL: lea_forced_large_data:
+; LARGE-STATIC: # %bb.0:
+; LARGE-STATIC-NEXT: movabsq $forced_large_data, %rax
+; LARGE-STATIC-NEXT: retq
+;
+; SMALL-PIC-LABEL: lea_forced_large_data:
+; SMALL-PIC: # %bb.0:
+; SMALL-PIC-NEXT: leaq _GLOBAL_OFFSET_TABLE_(%rip), %rax
+; SMALL-PIC-NEXT: leaq forced_large_data at GOTOFF(%rax), %rax
+; SMALL-PIC-NEXT: retq
+;
+; MEDIUM-SMALL-DATA-PIC-LABEL: lea_forced_large_data:
+; MEDIUM-SMALL-DATA-PIC: # %bb.0:
+; MEDIUM-SMALL-DATA-PIC-NEXT: leaq _GLOBAL_OFFSET_TABLE_(%rip), %rcx
+; MEDIUM-SMALL-DATA-PIC-NEXT: movabsq $forced_large_data at GOTOFF, %rax
+; MEDIUM-SMALL-DATA-PIC-NEXT: addq %rcx, %rax
+; MEDIUM-SMALL-DATA-PIC-NEXT: retq
+;
+; MEDIUM-PIC-LABEL: lea_forced_large_data:
+; MEDIUM-PIC: # %bb.0:
+; MEDIUM-PIC-NEXT: leaq _GLOBAL_OFFSET_TABLE_(%rip), %rcx
+; MEDIUM-PIC-NEXT: movabsq $forced_large_data at GOTOFF, %rax
+; MEDIUM-PIC-NEXT: addq %rcx, %rax
+; MEDIUM-PIC-NEXT: retq
+;
+; LARGE-PIC-LABEL: lea_forced_large_data:
+; LARGE-PIC: # %bb.0:
+; LARGE-PIC-NEXT: .L6$pb:
+; LARGE-PIC-NEXT: leaq .L6$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L6$pb, %rcx
+; LARGE-PIC-NEXT: addq %rax, %rcx
+; LARGE-PIC-NEXT: movabsq $forced_large_data at GOTOFF, %rax
+; LARGE-PIC-NEXT: addq %rcx, %rax
+; LARGE-PIC-NEXT: retq
+ ret ptr @forced_large_data
+}
+
+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: retq
+;
+; MEDIUM-STATIC-LABEL: load_forced_large_data:
+; MEDIUM-STATIC: # %bb.0:
+; MEDIUM-STATIC-NEXT: movabsq $forced_large_data, %rax
+; MEDIUM-STATIC-NEXT: movl 8(%rax), %eax
+; MEDIUM-STATIC-NEXT: retq
+;
+; LARGE-STATIC-LABEL: load_forced_large_data:
+; LARGE-STATIC: # %bb.0:
+; LARGE-STATIC-NEXT: movabsq $forced_large_data, %rax
+; LARGE-STATIC-NEXT: movl 8(%rax), %eax
+; LARGE-STATIC-NEXT: retq
+;
+; 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: retq
+;
+; MEDIUM-SMALL-DATA-PIC-LABEL: load_forced_large_data:
+; MEDIUM-SMALL-DATA-PIC: # %bb.0:
+; MEDIUM-SMALL-DATA-PIC-NEXT: leaq _GLOBAL_OFFSET_TABLE_(%rip), %rax
+; MEDIUM-SMALL-DATA-PIC-NEXT: movabsq $forced_large_data at GOTOFF, %rcx
+; MEDIUM-SMALL-DATA-PIC-NEXT: movl 8(%rax,%rcx), %eax
+; MEDIUM-SMALL-DATA-PIC-NEXT: retq
+;
+; MEDIUM-PIC-LABEL: load_forced_large_data:
+; MEDIUM-PIC: # %bb.0:
+; MEDIUM-PIC-NEXT: leaq _GLOBAL_OFFSET_TABLE_(%rip), %rax
+; MEDIUM-PIC-NEXT: movabsq $forced_large_data at GOTOFF, %rcx
+; MEDIUM-PIC-NEXT: movl 8(%rax,%rcx), %eax
+; MEDIUM-PIC-NEXT: retq
+;
+; LARGE-PIC-LABEL: load_forced_large_data:
+; LARGE-PIC: # %bb.0:
+; LARGE-PIC-NEXT: .L7$pb:
+; LARGE-PIC-NEXT: leaq .L7$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L7$pb, %rcx
+; LARGE-PIC-NEXT: addq %rax, %rcx
+; LARGE-PIC-NEXT: movabsq $forced_large_data at GOTOFF, %rax
+; LARGE-PIC-NEXT: movl 8(%rcx,%rax), %eax
+; LARGE-PIC-NEXT: retq
+ %rv = load i32, ptr getelementptr inbounds (i32, ptr @forced_large_data, i64 2)
+ ret i32 %rv
+}
+
define dso_local i32 @load_global_data() #0 {
; SMALL-STATIC-LABEL: load_global_data:
; SMALL-STATIC: # %bb.0:
@@ -261,9 +455,9 @@ define dso_local i32 @load_global_data() #0 {
;
; LARGE-PIC-LABEL: load_global_data:
; LARGE-PIC: # %bb.0:
-; LARGE-PIC-NEXT: .L4$pb:
-; LARGE-PIC-NEXT: leaq .L4$pb(%rip), %rax
-; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L4$pb, %rcx
+; LARGE-PIC-NEXT: .L8$pb:
+; LARGE-PIC-NEXT: leaq .L8$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L8$pb, %rcx
; LARGE-PIC-NEXT: addq %rax, %rcx
; LARGE-PIC-NEXT: movabsq $global_data at GOTOFF, %rax
; LARGE-PIC-NEXT: movl 8(%rcx,%rax), %eax
@@ -311,9 +505,9 @@ define dso_local i32 @load_extern_data() #0 {
;
; LARGE-PIC-LABEL: load_extern_data:
; LARGE-PIC: # %bb.0:
-; LARGE-PIC-NEXT: .L5$pb:
-; LARGE-PIC-NEXT: leaq .L5$pb(%rip), %rax
-; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L5$pb, %rcx
+; LARGE-PIC-NEXT: .L9$pb:
+; LARGE-PIC-NEXT: leaq .L9$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L9$pb, %rcx
; LARGE-PIC-NEXT: addq %rax, %rcx
; LARGE-PIC-NEXT: movabsq $extern_data at GOT, %rax
; LARGE-PIC-NEXT: movq (%rcx,%rax), %rax
@@ -362,9 +556,9 @@ define dso_local i32 @load_unknown_size_data() #0 {
;
; LARGE-PIC-LABEL: load_unknown_size_data:
; LARGE-PIC: # %bb.0:
-; LARGE-PIC-NEXT: .L6$pb:
-; LARGE-PIC-NEXT: leaq .L6$pb(%rip), %rax
-; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L6$pb, %rcx
+; LARGE-PIC-NEXT: .L10$pb:
+; LARGE-PIC-NEXT: leaq .L10$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L10$pb, %rcx
; LARGE-PIC-NEXT: addq %rax, %rcx
; LARGE-PIC-NEXT: movabsq $unknown_size_data at GOTOFF, %rax
; LARGE-PIC-NEXT: movl 8(%rcx,%rax), %eax
@@ -422,9 +616,9 @@ define dso_local ptr @lea_static_fn() #0 {
;
; LARGE-PIC-LABEL: lea_static_fn:
; LARGE-PIC: # %bb.0:
-; LARGE-PIC-NEXT: .L9$pb:
-; LARGE-PIC-NEXT: leaq .L9$pb(%rip), %rax
-; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L9$pb, %rcx
+; LARGE-PIC-NEXT: .L13$pb:
+; LARGE-PIC-NEXT: leaq .L13$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L13$pb, %rcx
; LARGE-PIC-NEXT: addq %rax, %rcx
; LARGE-PIC-NEXT: movabsq $static_fn at GOTOFF, %rax
; LARGE-PIC-NEXT: addq %rcx, %rax
@@ -465,9 +659,9 @@ define dso_local ptr @lea_global_fn() #0 {
;
; LARGE-PIC-LABEL: lea_global_fn:
; LARGE-PIC: # %bb.0:
-; LARGE-PIC-NEXT: .L10$pb:
-; LARGE-PIC-NEXT: leaq .L10$pb(%rip), %rax
-; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L10$pb, %rcx
+; LARGE-PIC-NEXT: .L14$pb:
+; LARGE-PIC-NEXT: leaq .L14$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L14$pb, %rcx
; LARGE-PIC-NEXT: addq %rax, %rcx
; LARGE-PIC-NEXT: movabsq $global_fn at GOTOFF, %rax
; LARGE-PIC-NEXT: addq %rcx, %rax
@@ -508,9 +702,9 @@ define dso_local ptr @lea_extern_fn() #0 {
;
; LARGE-PIC-LABEL: lea_extern_fn:
; LARGE-PIC: # %bb.0:
-; LARGE-PIC-NEXT: .L11$pb:
-; LARGE-PIC-NEXT: leaq .L11$pb(%rip), %rax
-; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L11$pb, %rcx
+; LARGE-PIC-NEXT: .L15$pb:
+; LARGE-PIC-NEXT: leaq .L15$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L15$pb, %rcx
; LARGE-PIC-NEXT: addq %rax, %rcx
; LARGE-PIC-NEXT: movabsq $extern_fn at GOT, %rax
; LARGE-PIC-NEXT: movq (%rcx,%rax), %rax
@@ -586,9 +780,9 @@ define dso_local float @load_constant_pool(float %x) #0 {
;
; LARGE-PIC-LABEL: load_constant_pool:
; LARGE-PIC: # %bb.0:
-; LARGE-PIC-NEXT: .L13$pb:
-; LARGE-PIC-NEXT: leaq .L13$pb(%rip), %rax
-; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L13$pb, %rcx
+; LARGE-PIC-NEXT: .L17$pb:
+; LARGE-PIC-NEXT: leaq .L17$pb(%rip), %rax
+; LARGE-PIC-NEXT: movabsq $_GLOBAL_OFFSET_TABLE_-.L17$pb, %rcx
; LARGE-PIC-NEXT: addq %rax, %rcx
; LARGE-PIC-NEXT: movabsq ${{\.?LCPI[0-9]+_[0-9]+}}@GOTOFF, %rax
; LARGE-PIC-NEXT: addss (%rcx,%rax), %xmm0
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