[llvm-branch-commits] [llvm] release/19.x: [RISCV] Don't delete all fixups in RISCVMCCodeEmitter::expandLongCondBr. (#109513) (PR #114089)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/114089

Backport c3d3cef8d58377b02032b07b5f094a402a70435a

Requested by: @topperc

>From 55446b4aa6610362e05181c9680c828a98ae34e9 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Sun, 22 Sep 2024 22:31:36 -0700
Subject: [PATCH] [RISCV] Don't delete all fixups in
 RISCVMCCodeEmitter::expandLongCondBr. (#109513)

The Fixups vector passed into this function may already have fixups in
it from earlier instructions. We should not erase those. We just want to
erase fixups added by this function.

Fixes #108612.

(cherry picked from commit c3d3cef8d58377b02032b07b5f094a402a70435a)
---
 llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp | 7 ++++++-
 llvm/test/MC/RISCV/rv64-relax-all.s                       | 6 ++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
index 0863345b0c6dc6..c9636b2c702508 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
@@ -283,13 +283,18 @@ void RISCVMCCodeEmitter::expandLongCondBr(const MCInst &MI,
     Offset = 4;
   }
 
+  // Save the number fixups.
+  size_t FixupStartIndex = Fixups.size();
+
   // Emit an unconditional jump to the destination.
   MCInst TmpInst =
       MCInstBuilder(RISCV::JAL).addReg(RISCV::X0).addOperand(SrcSymbol);
   uint32_t Binary = getBinaryCodeForInstr(TmpInst, Fixups, STI);
   support::endian::write(CB, Binary, llvm::endianness::little);
 
-  Fixups.clear();
+  // Drop any fixup added so we can add the correct one.
+  Fixups.resize(FixupStartIndex);
+
   if (SrcSymbol.isExpr()) {
     Fixups.push_back(MCFixup::create(Offset, SrcSymbol.getExpr(),
                                      MCFixupKind(RISCV::fixup_riscv_jal),
diff --git a/llvm/test/MC/RISCV/rv64-relax-all.s b/llvm/test/MC/RISCV/rv64-relax-all.s
index 70a3f77540c997..6705d6ecfb5b62 100644
--- a/llvm/test/MC/RISCV/rv64-relax-all.s
+++ b/llvm/test/MC/RISCV/rv64-relax-all.s
@@ -14,3 +14,9 @@ c.beqz a0, NEAR
 # INSTR:           c.j    0x0 <NEAR>
 # RELAX-INSTR:     jal    zero, 0x0 <NEAR>
 c.j NEAR
+
+bnez s0, .foo
+j    .foo
+beqz s0, .foo
+.foo:
+ret