From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22796 invoked by alias); 3 Jan 2006 23:01:18 -0000 Received: (qmail 22773 invoked by uid 48); 3 Jan 2006 23:01:16 -0000 Date: Tue, 03 Jan 2006 23:01:00 -0000 Subject: [Bug rtl-optimization/25654] New: [4.0/4.1/4.2 Regression] RTL alias analysis unprepared to handle stack slot sharing X-Bugzilla-Reason: CC Message-ID: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "steven at gcc dot gnu dot org" Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2006-01/txt/msg00305.txt.bz2 List-Id: In the following C code, the order of loads and stores is messed up, leading to wrong code: extern void abort (void) __attribute__((noreturn)); union setconflict { short a[20]; int b[10]; }; int main () { int sum = 0; { union setconflict a; short *c; c = a.a; asm ("": "=r" (c):"0" (c)); *c = 0; asm ("": "=r" (c):"0" (c)); sum += *c; } { union setconflict a; int *c; c = a.b; asm ("": "=r" (c):"0" (c)); *c = 1; asm ("": "=r" (c):"0" (c)); sum += *c; } printf ("%d\n",sum); if (sum != 1) abort(); return 0; } .file "t.c" # GNU C version 4.2.0 20060101 (experimental) (x86_64-unknown-linux-gnu) # compiled by GNU C version 4.0.2 20050901 (prerelease) (SUSE Linux). # GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096 # options passed: -iprefix -isystem -m32 -march=pentiumpro -auxbase -O2 # -fdump-tree-vars -fomit-frame-pointer -fverbose-asm # options enabled: -falign-loops -fargument-alias -fbranch-count-reg # -fcaller-saves -fcommon -fcprop-registers -fcrossjumping # -fcse-follow-jumps -fcse-skip-blocks -fdefer-pop # -fdelete-null-pointer-checks -fearly-inlining # -feliminate-unused-debug-types -fexpensive-optimizations -ffunction-cse # -fgcse -fgcse-lm -fguess-branch-probability -fident -fif-conversion # -fif-conversion2 -finline-functions-called-once -fipa-pure-const # -fipa-reference -fipa-type-escape -fivopts -fkeep-static-consts # -fleading-underscore -floop-optimize -floop-optimize2 -fmath-errno # -fmerge-constants -fomit-frame-pointer -foptimize-register-move # -foptimize-sibling-calls -fpcc-struct-return -fpeephole -fpeephole2 # -fregmove -freorder-blocks -freorder-functions -frerun-cse-after-loop # -frerun-loop-opt -fsched-interblock -fsched-spec # -fsched-stalled-insns-dep -fschedule-insns2 -fshow-column # -fsplit-ivs-in-unroller -fstrength-reduce -fstrict-aliasing # -fthread-jumps -ftrapping-math -ftree-ccp -ftree-ch -ftree-copy-prop # -ftree-copyrename -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-fre # -ftree-loop-im -ftree-loop-ivcanon -ftree-loop-optimize -ftree-lrs # -ftree-pre -ftree-salias -ftree-sink -ftree-sra -ftree-store-ccp # -ftree-store-copy-prop -ftree-ter -ftree-vect-loop-version -ftree-vrp # -funit-at-a-time -fverbose-asm -fzero-initialized-in-bss -m32 -m80387 # -m96bit-long-double -maccumulate-outgoing-args -malign-stringops # -mfancy-math-387 -mfp-ret-in-387 -mieee-fp -mno-red-zone -mpush-args # -mtls-direct-seg-refs # Compiler executable checksum: 6d90f1c30ff8027bc6976ab2dbfe2320 .section .rodata.str1.1,"aMS",@progbits,1 .LC0: .string "%d\n" .text .p2align 4,,15 .globl main .type main, @function main: leal 4(%esp), %ecx #, andl $-16, %esp #, pushl -4(%ecx) # subl $76, %esp #, leal 28(%esp), %eax #, tmp64 movl %ecx, 68(%esp) #, movl %eax, %edx # tmp64, c movl %ebx, 72(%esp) #, movw $0, (%edx) #,* c movl $1, (%eax) #,* c movswl (%edx),%ebx #* c, sum movl (%eax), %edx #* c, movl $.LC0, (%esp) #, addl %edx, %ebx #, sum movl %ebx, 4(%esp) # sum, call printf # decl %ebx # sum jne .L6 #, movl 68(%esp), %ecx #, xorl %eax, %eax # movl 72(%esp), %ebx #, addl $76, %esp #, leal -4(%ecx), %esp #, ret .L6: call abort # .size main, .-main .ident "GCC: (GNU) 4.2.0 20060101 (experimental)" .section .note.GNU-stack,"",@progbits See also the thread on the gcc@ mailing list starting here: http://gcc.gnu.org/ml/gcc/2006-01/msg00008.html. -- Summary: [4.0/4.1/4.2 Regression] RTL alias analysis unprepared to handle stack slot sharing Product: gcc Version: 4.2.0 Status: UNCONFIRMED Keywords: wrong-code, alias Severity: major Priority: P3 Component: rtl-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: steven at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25654