[lld] [RISCV][lld] Guarding lld relaxation for RISCV (PR #130265)

[Sharjeel Khan via llvm-commits]

https://github.com/Sharjeel-Khan updated https://github.com/llvm/llvm-project/pull/130265

>From a50db56d2db08707632b7b3d9cb5171294dd170c Mon Sep 17 00:00:00 2001
From: Sharjeel Khan <sharjeelkhan at google.com>
Date: Fri, 7 Mar 2025 08:38:38 +0000
Subject: [PATCH 1/2] [RISCV][lld] Gurading lld relaxation for RISCV

Based on the
[comment](https://github.com/llvm/llvm-project/issues/123248#issuecomment-2675911618),
the relaxation algorithm assumes relaxing a call will shift the later
function forward by the same bytes we removed. As some sections are
between call and its call target are 32-byte aligned, the call and call
target sections might not be the same distance apart. We guard band the
relaxation so it stops the relaxation loop and take the last state.
---
 lld/ELF/Arch/RISCV.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lld/ELF/Arch/RISCV.cpp b/lld/ELF/Arch/RISCV.cpp
index 4d8989a21b501..c8a9a7093719e 100644
--- a/lld/ELF/Arch/RISCV.cpp
+++ b/lld/ELF/Arch/RISCV.cpp
@@ -901,6 +901,9 @@ bool RISCV::relaxOnce(int pass) const {
   llvm::TimeTraceScope timeScope("RISC-V relaxOnce");
   if (ctx.arg.relocatable)
     return false;
+  
+  if (pass == 29)
+    return false;
 
   if (pass == 0)
     initSymbolAnchors(ctx);

>From 6bc9d11eb4c07e4291eaa28f7b4bac38b7f446b6 Mon Sep 17 00:00:00 2001
From: Sharjeel Khan <sharjeelkhan at google.com>
Date: Fri, 7 Mar 2025 08:38:38 +0000
Subject: [PATCH 2/2] [RISCV][lld] Guarding lld relaxation for RISCV

Based on https://github.com/llvm/llvm-project/issues/123248#issuecomment-2675911618,
the relaxation algorithm assumes relaxing a call will shift the later
function forward by the same bytes we removed. As some sections are
between call and its call target are 32-byte aligned, the call and call
target sections might not be the same distance apart. We guard band the
relaxation so it stops the relaxation loop and take the last state.
---
 lld/ELF/Arch/RISCV.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lld/ELF/Arch/RISCV.cpp b/lld/ELF/Arch/RISCV.cpp
index c8a9a7093719e..8100b6ddd1934 100644
--- a/lld/ELF/Arch/RISCV.cpp
+++ b/lld/ELF/Arch/RISCV.cpp
@@ -901,7 +901,10 @@ bool RISCV::relaxOnce(int pass) const {
   llvm::TimeTraceScope timeScope("RISC-V relaxOnce");
   if (ctx.arg.relocatable)
     return false;
-  
+
+  if (pass == 29)
+    return false;
+
   if (pass == 29)
     return false;