[PATCH] D125272: [clang] Add -fcheck-new support

Mon May 9 17:48:46 PDT 2022

jrtc27 added inline comments.

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Comment at: clang/test/CodeGenCXX/fcheck-new.cpp:2
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang -fcheck-new -emit-llvm -S %s -o - -O2 | FileCheck %s
+
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heatd wrote:
> jrtc27 wrote:
> > Do you really want -O2 or do you just want to run mem2reg to eliminate all the alloca noise?
> I added -O2 because I was testing with it, since if -fcheck-new doesn't work, it's way more noticeable, as the nullptr check gets optimized out; if it works, the branching is pretty visible and shows exactly what the option does. Also, to eliminate all the noise :) I can definitely remove -O2 though, if you want to.
Thinking about this more, I think the branching complicates matters. All that optimisation happens in LLVM IR land, but you're just touching Clang CodeGen. Is `int *foo() { return new int; }` checking the attributes on the call to _Znwm not enough (and with mem2reg just to clean it up so the function body is trivial)?

Also you should specify a target triple as this will just be LLVM_DEFAULT_TARGET_TRIPLE and change both the type for new (i32 vs i64) and its mangling (j vs m for unsigned int vs unsigned long, and *-windows-msvc is totally different), right?

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Comment at: clang/test/CodeGenCXX/fcheck-new.cpp:9
+// CHECK:       3:
+// CHECK-NEXT:    store i32 48879, ptr [[TMP1]], align 4, !tbaa [[TBAA5:![0-9]+]]
+// CHECK-NEXT:    br label [[TMP4]]
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Another advantage of not using -O2 is you lose the TBAA noise

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Comment at: clang/test/Driver/clang_f_opts.c:73

-
 // RUN: %clang -### -S -fauto-profile=%S/Inputs/file.prof %s 2>&1 | FileCheck -check-prefix=CHECK-AUTO-PROFILE %s
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Hmmm

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D125272/new/

https://reviews.llvm.org/D125272