From 7f3e822efb1bee779f8a520c5efb48ce33d1bfef Mon Sep 17 00:00:00 2001
From: Joel Rosdahl <joel@rosdahl.net>
Date: Tue, 9 Dec 2025 19:19:17 +0100
Subject: [PATCH] fix: Avoid hashing CWD parts of -march=native expansion for
 Clang

Fixes #1658.
---
 src/ccache/ccache.cpp                     | 32 ++++++++++++++++++++---
 test/fake-compilers/clang-march-native.sh |  2 +-
 test/suites/base.bash                     | 17 ++++++++++++
 3 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/src/ccache/ccache.cpp b/src/ccache/ccache.cpp
index b44296db..7aa40c65 100644
--- a/src/ccache/ccache.cpp
+++ b/src/ccache/ccache.cpp
@@ -2045,10 +2045,34 @@ hash_native_args(Context& ctx, const util::Args& native_args, Hash& hash)
 
   hash.hash_delimiter(native_args.to_string());
 
-  // We could potentially work out exactly which options -m*=native expand to
-  // and hash only those, but to keep things simple we include the full line
-  // where cc1 was found for now.
-  hash.hash(*line_to_hash);
+  if (ctx.config.is_compiler_group_clang()) {
+    // For Clang, extract and hash only architecture-related options to avoid
+    // hashing CWD-dependent paths like -fdebug-compilation-dir and
+    // -fcoverage-compilation-dir which cause cache misses when compiling from
+    // different directories.
+    //
+    // We specifically look for:
+    //
+    // - "-target-cpu" followed by CPU name (e.g., "alderlake")
+    // - "-tune-cpu" followed by CPU name
+    // - "-target-feature" followed by feature flag (e.g., "+avx2", "-avx512f")
+    bool hash_value = false;
+    for (const auto token : util::Tokenizer(*line_to_hash, " ")) {
+      if (hash_value) {
+        hash.hash(' ');
+        hash.hash(token);
+        hash_value = false;
+      } else if (token == "\"-target-cpu\"" || token == "\"-tune-cpu\""
+                 || token == "\"-target-feature\"") {
+        hash.hash(token);
+        hash_value = true;
+      }
+    }
+  } else {
+    // For GCC, the full line should be safe to hash as it doesn't contain
+    // CWD-dependent paths.
+    hash.hash(*line_to_hash);
+  }
 
   return {};
 }
diff --git a/test/fake-compilers/clang-march-native.sh b/test/fake-compilers/clang-march-native.sh
index 32d6a7b5..e7f25776 100755
--- a/test/fake-compilers/clang-march-native.sh
+++ b/test/fake-compilers/clang-march-native.sh
@@ -7,7 +7,7 @@ if [ "$1" = "-###" ]; then
 ...
 InstalledDir: /usr/bin
  (in-process)
- "/example/bin/clang" "-cc1" $CC1_ARGS
+ "/example/bin/clang" "-cc1" "-target-cpu" "$CC1_ARGS"
 EOF
     echo "bin/cc1"
 elif [ "$1" = "-E" ]; then
diff --git a/test/suites/base.bash b/test/suites/base.bash
index cdb7daff..e6ed77e9 100644
--- a/test/suites/base.bash
+++ b/test/suites/base.bash
@@ -1702,6 +1702,23 @@ EOF
     expect_stat preprocessed_cache_hit 2
     expect_stat cache_miss 2
 
+    # -------------------------------------------------------------------------
+    if $COMPILER -march=native -c test1.c 2>/dev/null; then
+        TEST "-march=native, no CWD in input hash"
+        mkdir a b
+        cp test1.c a
+        cp test1.c b
+        cd a
+        $CCACHE_COMPILE -march=native -c test1.c
+        expect_stat preprocessed_cache_hit 0
+        expect_stat cache_miss 1
+        cd ../b
+        $CCACHE_COMPILE -march=native -c test1.c
+        cd ..
+        expect_stat preprocessed_cache_hit 1
+        expect_stat cache_miss 1
+    fi
+
     # -------------------------------------------------------------------------
     TEST "Handling of compiler-only arguments"
 
-- 
2.47.3