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From: "hubicka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/103674] New: Poor codegen for C++ casts Date: Sun, 12 Dec 2021 20:10:51 +0000 [thread overview] Message-ID: <bug-103674-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103674 Bug ID: 103674 Summary: Poor codegen for C++ casts Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: hubicka at gcc dot gnu.org Target Milestone: --- Compiling: struct a {int a;}; struct b {int b;}; struct c : a, b {}; int test(struct c *c) { struct b *b=c; return b->b; } with -O2 leads to: .text .LHOTB0: .p2align 4 .globl _Z4testP1c .type _Z4testP1c, @function _Z4testP1c: .LFB0: .cfi_startproc testq %rdi, %rdi je .L2 movl 4(%rdi), %eax ret .cfi_endproc .section .text.unlikely .cfi_startproc .type _Z4testP1c.cold, @function _Z4testP1c.cold: .LFSB0: .L2: movl 0, %eax ud2 .cfi_endproc .LFE0: while clang does: _Z4testP1c: # @_Z4testP1c .cfi_startproc # %bb.0: leaq 4(%rdi), %rax testq %rdi, %rdi cmoveq %rdi, %rax movl (%rax), %eax retq And so does gcc 4.8.5: test(c*): leaq 4(%rdi), %rdx xorl %eax, %eax testq %rdi, %rdi cmovne %rdx, %rax movl (%rax), %eax ret So this is technically a regression.
next reply other threads:[~2021-12-12 20:10 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-12-12 20:10 hubicka at gcc dot gnu.org [this message] 2021-12-13 11:05 ` [Bug tree-optimization/103674] " hubicka at gcc dot gnu.org
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