DAGCombine add (sext i1), X into sub X, (zext i1) if sext from i1 is illegal. ...
DAGCombine add (sext i1), X into sub X, (zext i1) if sext from i1 is illegal. The latter usually compiles into smaller code. example code: unsigned foo(unsigned x, unsigned y) { if (x != 0) y--; return y; } before: _foo: ## @foo cmpl $1, 4(%esp) ## encoding: [0x83,0x7c,0x24,0x04,0x01] sbbl %eax, %eax ## encoding: [0x19,0xc0] notl %eax ## encoding: [0xf7,0xd0] addl 8(%esp), %eax ## encoding: [0x03,0x44,0x24,0x08] ret ## encoding: [0xc3] after: _foo: ## @foo cmpl $1, 4(%esp) ## encoding: [0x83,0x7c,0x24,0x04,0x01] movl 8(%esp), %eax ## encoding: [0x8b,0x44,0x24,0x08] adcl $-1, %eax ## encoding: [0x83,0xd0,0xff] ret ## encoding: [0xc3] llvm-svn: 122455
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