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Revert "[Clang] Enable -fextend-lifetimes at -Og (#118026)"

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Reverted following several issues appearing related to fake uses, reported
on the github PR.

This reverts commit a9dff35ad2.
This commit is contained in:
Stephen Tozer
2025-04-25 12:18:26 +01:00
parent accee2b553
commit 2dc6e98169
4 changed files with 4 additions and 18 deletions
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7
clang/docs/CommandGuide/clang.rst
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@@ -443,11 +443,8 @@ Code Generation Options
:option:`-Oz` Like :option:`-Os` (and thus :option:`-O2`), but reduces code
size further.
:option:`-Og` Similar to :option:`-O1`, but with slightly reduced
optimization and better variable visibility. The same optimizations are run
as at :option:`-O1`, but the ``-fextend-variable-liveness`` flag is
also set, which tries to prevent optimizations from reducing the liveness of
user variables, improving their availability when debugging.
:option:`-Og` Like :option:`-O1`. In future versions, this option might
disable different optimizations in order to improve debuggability.
:option:`-O` Equivalent to :option:`-O1`.

4
clang/docs/ReleaseNotes.rst
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@@ -230,10 +230,6 @@ Modified Compiler Flags
- The ``-mexecute-only`` and ``-mpure-code`` flags are now accepted for AArch64 targets. (#GH125688)
- The ``-Og`` optimization flag now sets ``-fextend-variable-liveness``,
reducing performance slightly while reducing the number of optimized-out
variables.
Removed Compiler Flags
-------------------------

8
clang/lib/Driver/ToolChains/Clang.cpp
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@@ -7683,13 +7683,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
if (Args.hasArg(options::OPT_fretain_comments_from_system_headers))
CmdArgs.push_back("-fretain-comments-from-system-headers");
if (Arg *A = Args.getLastArg(options::OPT_fextend_variable_liveness_EQ)) {
A->render(Args, CmdArgs);
} else if (Arg *A = Args.getLastArg(options::OPT_O_Group);
A && A->containsValue("g")) {
// Set -fextend-variable-liveness=all by default at -Og.
CmdArgs.push_back("-fextend-variable-liveness=all");
}
Args.AddLastArg(CmdArgs, options::OPT_fextend_variable_liveness_EQ);
// Forward -fcomment-block-commands to -cc1.
Args.AddAllArgs(CmdArgs, options::OPT_fcomment_block_commands);

3
clang/test/Driver/extend-variable-liveness.c
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@@ -1,8 +1,7 @@
// Tests that -fextend-variable-liveness and its aliases are correctly passed
// by the driver, and are set by default at -Og.
// by the driver.
// RUN: %clang -### -c %s 2>&1 | FileCheck %s --check-prefixes=CHECK,DEFAULT
// RUN: %clang -### -Og -c %s 2>&1 | FileCheck %s --check-prefixes=CHECK,ALL
// RUN: %clang -fextend-variable-liveness=none -### -c %s 2>&1 | FileCheck %s --check-prefixes=CHECK,NONE
// RUN: %clang -fextend-variable-liveness=this -### -c %s 2>&1 | FileCheck %s --check-prefixes=CHECK,THIS
// RUN: %clang -fextend-variable-liveness=all -### -c %s 2>&1 | FileCheck %s --check-prefixes=CHECK,ALL