These two testcases should produce equivalent code: int test(int a, int b) { int lt = a < b; int eq = a == b;
return (lt || eq); } int test_(int a, int b) { return (a < b || a == b); } However, the optimized tree code is: ;; Function test (test) Analyzing Edge Insertions. test (a, b) { <bb 2>: return (a == b | a < b) != 0; } ;; Function test_ (test_) Analyzing Edge Insertions. test_ (a, b) { <bb 2>: return a <= b; } And the resultinh x86_64 asm is unoptimal for test() function: test: cmpl %esi, %edi sete %dl cmpl %esi, %edi setl %al orl %edx, %eax movzbl %al, %eax ret test_: xorl %eax, %eax cmpl %esi, %edi setle %al ret -- Summary: Multiple comparisons are not simplified Product: gcc Version: 4.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: middle-end AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: uros at kss-loka dot si GCC build triplet: x86_64-pc-linux-gnu GCC host triplet: x86_64-pc-linux-gnu GCC target triplet: x86_64-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28685