[llvm] 5f449b9 - [RISCV] Allow RISCVMCExpr folding in the absence of linker relaxaxation

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2025-03-15T11:25:30-07:00
New Revision: 5f449b9a5dae35afc88c825a0703e348f47e5875

URL: https://github.com/llvm/llvm-project/commit/5f449b9a5dae35afc88c825a0703e348f47e5875
DIFF: https://github.com/llvm/llvm-project/commit/5f449b9a5dae35afc88c825a0703e348f47e5875.diff

LOG: [RISCV] Allow RISCVMCExpr folding in the absence of linker relaxaxation

In the AArch64 target, `bar: add x0, x0, :lo12:foo-bar; foo:`
can be folded.

Remove the restriction (https://reviews.llvm.org/D104473), which became
unnecessary after https://reviews.llvm.org/D155357

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp
    llvm/test/MC/RISCV/hilo-constaddr-expr.s

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp
index 99a31054a4e81..aa04ec23c60a1 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp
@@ -91,10 +91,7 @@ const MCFixup *RISCVMCExpr::getPCRelHiFixup(const MCFragment **DFOut) const {
 bool RISCVMCExpr::evaluateAsRelocatableImpl(MCValue &Res,
                                             const MCAssembler *Asm,
                                             const MCFixup *Fixup) const {
-  // Explicitly drop the layout and assembler to prevent any symbolic folding in
-  // the expression handling.  This is required to preserve symbolic 
diff erence
-  // expressions to emit the paired relocations.
-  if (!getSubExpr()->evaluateAsRelocatable(Res, nullptr, nullptr))
+  if (!getSubExpr()->evaluateAsRelocatable(Res, Asm, Fixup))
     return false;
 
   Res =

diff  --git a/llvm/test/MC/RISCV/hilo-constaddr-expr.s b/llvm/test/MC/RISCV/hilo-constaddr-expr.s
index 8dc38702a2472..3cc10bb12e441 100644
--- a/llvm/test/MC/RISCV/hilo-constaddr-expr.s
+++ b/llvm/test/MC/RISCV/hilo-constaddr-expr.s
@@ -1,10 +1,15 @@
 # RUN: not llvm-mc -filetype=obj -triple=riscv32 -mattr=+relax %s -o /dev/null 2>&1 | FileCheck %s
-# RUN: not llvm-mc -filetype=obj -triple=riscv32 -mattr=-relax %s -o /dev/null 2>&1 | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple=riscv32 -mattr=-relax %s | llvm-objdump -d - | FileCheck %s --check-prefix=NORELAX
 
 # Check the assembler rejects hi and lo expressions with constant expressions
 # involving labels when 
diff  expressions are emitted as relocation pairs.
 # Test case derived from test/MC/Mips/hilo-addressing.s
 
+# NORELAX:      lui t0, 0x0
+# NORELAX-NEXT: lw ra, 0x8(t0)
+# NORELAX:      lui t1, 0x0
+# NORELAX-NEXT: lw sp, -0x8(t1)
+
 tmp1:
 tmp2:
 # CHECK: :[[#@LINE+1]]:[[#]]: error: expected relocatable expression