GCC modified for the FreeChainXenon project
b3e98eb339
This patch fixes PR tree-optimization/102950, which is a P2 regression, by providing better range bounds for BIT_XOR_EXPR, BIT_AND_EXPR and BIT_IOR_EXPR on signed integer types. In general terms, any binary bitwise operation on sign-extended or zero-extended integer types will produce results that are themselves sign-extended or zero-extended. More precisely, we can derive signed bounds from the number of leading redundant sign bit copies, from the equation: clrsb(X op Y) >= min (clrsb (X), clrsb(Y)) and from the property that for any (signed or unsigned) range [lb, ub] that clrsb([lb, ub]) >= min (clrsb(lb), clrsb(ub)). These can be used to show that [-1, 0] op [-1, 0] is [-1, 0] or that [-128, 127] op [-128, 127] is [-128, 127], even when tracking nonzero bits would result in VARYING (as every bit can be 0 or 1). This is equivalent to determining the minimum type precision in which the operation can be performed then sign extending the result. One additional refinement is to observe that X ^ Y can never be zero if the ranges of X and Y don't overlap, i.e. X can't be equal to Y. Previously, the expression "(int)(char)a ^ 233" in the PR was considered VARYING, but with the above changes now has the range [-256, -1][1, 255], which is sufficient to optimize away the call to foo. 2022-05-03 Roger Sayle <roger@nextmovesoftware.com> gcc/ChangeLog PR tree-optimization/102950 * range-op.cc (wi_optimize_signed_bitwise_op): New function to determine bounds of bitwise operations on signed types. (operator_bitwise_and::wi_fold): Call the above function. (operator_bitwise_or::wi_fold): Likewise. (operator_bitwise_xor::wi_fold): Likewise. Additionally, the result can't be zero if the operands can't be equal. gcc/testsuite/ChangeLog PR tree-optimization/102950 * gcc.dg/pr102950.c: New test case. * gcc.dg/tree-ssa/evrp10.c: New test case. |
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| c++tools | ||
| config | ||
| contrib | ||
| fixincludes | ||
| gcc | ||
| gnattools | ||
| gotools | ||
| include | ||
| INSTALL | ||
| intl | ||
| libada | ||
| libatomic | ||
| libbacktrace | ||
| libcc1 | ||
| libcody | ||
| libcpp | ||
| libdecnumber | ||
| libffi | ||
| libgcc | ||
| libgfortran | ||
| libgo | ||
| libgomp | ||
| libiberty | ||
| libitm | ||
| libobjc | ||
| liboffloadmic | ||
| libphobos | ||
| libquadmath | ||
| libsanitizer | ||
| libssp | ||
| libstdc++-v3 | ||
| libvtv | ||
| lto-plugin | ||
| maintainer-scripts | ||
| zlib | ||
| .dir-locals.el | ||
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| ABOUT-NLS | ||
| ar-lib | ||
| ChangeLog | ||
| ChangeLog.jit | ||
| ChangeLog.tree-ssa | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
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| COPYING.RUNTIME | ||
| COPYING3 | ||
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| depcomp | ||
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| MAINTAINERS | ||
| Makefile.def | ||
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| missing | ||
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| move-if-change | ||
| multilib.am | ||
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