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ce7cafa960
two or three, open code the equivalent operation which is faster on athlon and P4 (by a substantial margin). For example, instead of compiling this: long long X2(long long Y) { return Y << 2; } to: X3_2: movl 4(%esp), %eax movl 8(%esp), %edx shldl $2, %eax, %edx shll $2, %eax ret Compile it to: X2: movl 4(%esp), %eax movl 8(%esp), %ecx movl %eax, %edx shrl $30, %edx leal (%edx,%ecx,4), %edx shll $2, %eax ret Likewise, for << 3, compile to: X3: movl 4(%esp), %eax movl 8(%esp), %ecx movl %eax, %edx shrl $29, %edx leal (%edx,%ecx,8), %edx shll $3, %eax ret This matches icc, except that icc open codes the shifts as adds on the P4. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17707 91177308-0d34-0410-b5e6-96231b3b80d8 |
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