[llvm] [X86][FastISel] Support medium code model in more places (PR #75375)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Arthur Eubanks (aeubanks)

<details>
<summary>Changes</summary>

The medium code model is basically identical to the small code model
except that large objects cannot be referenced with 32-bit offsets.


---
Full diff: https://github.com/llvm/llvm-project/pull/75375.diff


3 Files Affected:

- (modified) llvm/lib/Target/X86/X86FastISel.cpp (+12-6) 
- (modified) llvm/test/CodeGen/X86/fast-isel-constpool.ll (+1) 
- (added) llvm/test/CodeGen/X86/fast-isel-medium-code-model.ll (+44) 


``````````diff
diff --git a/llvm/lib/Target/X86/X86FastISel.cpp b/llvm/lib/Target/X86/X86FastISel.cpp
index bdc9d1d42dd160..425c52dbe7b104 100644
--- a/llvm/lib/Target/X86/X86FastISel.cpp
+++ b/llvm/lib/Target/X86/X86FastISel.cpp
@@ -711,7 +711,8 @@ bool X86FastISel::handleConstantAddresses(const Value *V, X86AddressMode &AM) {
   // Handle constant address.
   if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
     // Can't handle alternate code models yet.
-    if (TM.getCodeModel() != CodeModel::Small)
+    if (TM.getCodeModel() != CodeModel::Small &&
+        TM.getCodeModel() != CodeModel::Medium)
       return false;
 
     // Can't handle large objects yet.
@@ -1050,7 +1051,8 @@ bool X86FastISel::X86SelectCallAddress(const Value *V, X86AddressMode &AM) {
   // Handle constant address.
   if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
     // Can't handle alternate code models yet.
-    if (TM.getCodeModel() != CodeModel::Small)
+    if (TM.getCodeModel() != CodeModel::Small &&
+        TM.getCodeModel() != CodeModel::Medium)
       return false;
 
     // RIP-relative addresses can't have additional register operands.
@@ -3774,7 +3776,8 @@ unsigned X86FastISel::X86MaterializeFP(const ConstantFP *CFP, MVT VT) {
 
   // Can't handle alternate code models yet.
   CodeModel::Model CM = TM.getCodeModel();
-  if (CM != CodeModel::Small && CM != CodeModel::Large)
+  if (CM != CodeModel::Small && CM != CodeModel::Medium &&
+      CM != CodeModel::Large)
     return 0;
 
   // Get opcode and regclass of the output for the given load instruction.
@@ -3812,7 +3815,7 @@ unsigned X86FastISel::X86MaterializeFP(const ConstantFP *CFP, MVT VT) {
     PICBase = getInstrInfo()->getGlobalBaseReg(FuncInfo.MF);
   else if (OpFlag == X86II::MO_GOTOFF)
     PICBase = getInstrInfo()->getGlobalBaseReg(FuncInfo.MF);
-  else if (Subtarget->is64Bit() && TM.getCodeModel() == CodeModel::Small)
+  else if (Subtarget->is64Bit() && TM.getCodeModel() != CodeModel::Large)
     PICBase = X86::RIP;
 
   // Create the load from the constant pool.
@@ -3842,8 +3845,11 @@ unsigned X86FastISel::X86MaterializeFP(const ConstantFP *CFP, MVT VT) {
 }
 
 unsigned X86FastISel::X86MaterializeGV(const GlobalValue *GV, MVT VT) {
-  // Can't handle alternate code models yet.
-  if (TM.getCodeModel() != CodeModel::Small)
+  // Can't handle large GlobalValues yet.
+  if (TM.getCodeModel() != CodeModel::Small &&
+      TM.getCodeModel() != CodeModel::Medium)
+    return 0;
+  if (!isa<GlobalObject>(GV) || TM.isLargeGlobalObject(cast<GlobalObject>(GV)))
     return 0;
 
   // Materialize addresses with LEA/MOV instructions.
diff --git a/llvm/test/CodeGen/X86/fast-isel-constpool.ll b/llvm/test/CodeGen/X86/fast-isel-constpool.ll
index 9f70fd55907377..9e4cbb61308eaa 100644
--- a/llvm/test/CodeGen/X86/fast-isel-constpool.ll
+++ b/llvm/test/CodeGen/X86/fast-isel-constpool.ll
@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -mtriple=x86_64-apple-darwin -fast-isel -code-model=small < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-apple-darwin -fast-isel -code-model=medium < %s | FileCheck %s
 ; RUN: llc -mtriple=x86_64-apple-darwin -fast-isel -code-model=large < %s | FileCheck %s --check-prefix=LARGE
 ; RUN: llc -mtriple=x86_64 -fast-isel -code-model=large -relocation-model=pic < %s | FileCheck %s --check-prefix=LARGE_PIC
 ; RUN: llc -mtriple=x86_64-apple-darwin -fast-isel -code-model=small -mattr=avx < %s | FileCheck %s --check-prefix=AVX
diff --git a/llvm/test/CodeGen/X86/fast-isel-medium-code-model.ll b/llvm/test/CodeGen/X86/fast-isel-medium-code-model.ll
new file mode 100644
index 00000000000000..4aa230a209e285
--- /dev/null
+++ b/llvm/test/CodeGen/X86/fast-isel-medium-code-model.ll
@@ -0,0 +1,44 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=x86_64-linux-gnu -fast-isel -fast-isel-abort=3 -code-model=medium -large-data-threshold=5 < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-linux-gnu -fast-isel -code-model=medium -large-data-threshold=3 < %s -o /dev/null \
+; RUN:   -pass-remarks-output=- -pass-remarks-filter=sdagisel | FileCheck %s --check-prefix=FALLBACK --implicit-check-not=missed
+
+declare void @foo()
+
+define void @call_foo() {
+; CHECK-LABEL: call_foo:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    callq foo at PLT
+; CHECK-NEXT:    popq %rax
+; CHECK-NEXT:    .cfi_def_cfa_offset 8
+; CHECK-NEXT:    retq
+  call void @foo()
+  ret void
+}
+
+ at g = internal global i32 42
+
+; FALLBACK: FastISel missed terminator
+; FALLBACK: in function: g_addr
+
+define ptr @g_addr() {
+; CHECK-LABEL: g_addr:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movabsq $g, %rax
+; CHECK-NEXT:    retq
+  ret ptr @g
+}
+
+; FALLBACK: FastISel missed
+; FALLBACK: in function: load_g
+
+define i32 @load_g() {
+; CHECK-LABEL: load_g:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movl g, %eax
+; CHECK-NEXT:    retq
+  %i = load i32, ptr @g
+  ret i32 %i
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/75375