[SystemZ][z/OS] Fix "relative immediate relocation section mismatch"

[redstar]

Constants should go inside the text section, but this is not explicitly coded. In the test case, the EH table is generated into a PR section. Then the constant pool of function fn_with_const_pool() is emitted, which goes into the PR section of the EH table instead of the code section. When the constant is later referenced in the code, the relative offset cannot be calculated because different sections are involved.
The fix is to explicitly return the text section for constants.

[llvmorg-github-actions]

@llvm/pr-subscribers-backend-systemz

Author: Kai Nacke (redstar)

Changes

Constants should go inside the text section, but this is not explicitly coded. In the test case, the EH table is generated into a PR section. Then the constant pool of function fn_with_const_pool() is emitted, which goes into the PR section of the EH table instead of the code section. When the constant is later referenced in the code, the relative offset cannot be calculated because different sections are involved.
The fix is to explicitly return the text section for constants.

---

Full diff: https://github.com/llvm/llvm-project/pull/222437.diff

3 Files Affected:

• (modified) llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h (+3)
• (modified) llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (+6)
• (modified) llvm/test/CodeGen/SystemZ/zos-eh.ll (+5)

diff --git a/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h b/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
index af6eb0269378a..e631d820eb637 100644
--- a/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
+++ b/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
@@ -333,6 +333,9 @@ class LLVM_ABI TargetLoweringObjectFileGOFF : public TargetLoweringObjectFile {
 
   bool shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,
                                            const Function &F) const override;
+  MCSection *getSectionForConstant(const DataLayout &DL, SectionKind Kind,
+                                   const Constant *C, Align &Alignment,
+                                   const Function *F) const override;
   MCSection *SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind,
                                     const TargetMachine &TM) const override;
   MCSection *getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind,
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 4643ef995afec..2fb44041c164e 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -2860,6 +2860,12 @@ bool TargetLoweringObjectFileGOFF::shouldPutJumpTableInFunctionSection(
   return true;
 }
 
+MCSection *TargetLoweringObjectFileGOFF::getSectionForConstant(
+    const DataLayout &DL, SectionKind Kind, const Constant *C, Align &Alignment,
+    const Function *F) const {
+  return TextSection;
+}
+
 MCSection *TargetLoweringObjectFileGOFF::getExplicitSectionGlobal(
     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
   return SelectSectionForGlobal(GO, Kind, TM);
diff --git a/llvm/test/CodeGen/SystemZ/zos-eh.ll b/llvm/test/CodeGen/SystemZ/zos-eh.ll
index 9439289bfbd6b..a424de3068d9e 100644
--- a/llvm/test/CodeGen/SystemZ/zos-eh.ll
+++ b/llvm/test/CodeGen/SystemZ/zos-eh.ll
@@ -13,6 +13,11 @@ bb1:
   ret { ptr, i32 } zeroinitializer
 }
 
+define double @fn_with_const_pool() {
+start:
+  ret double 1.0   ; forces a constant pool entry (L#CPI1_0)
+}
+
 declare i32 @__zos_cxx_personality_v2(...)
 
 ; CHECK:      C_WSA64 CATTR ALIGN(2),FILL(0),NOTEXECUTABLE,RMODE(64),PART(.gcc_excepti

[uweigand]

LGTM, thanks!