[Bug rtl-optimization/114902] [14 Regression] wrong code at -O3 with "-fno-tree-vrp -fno-expensive-optimizations -fno-tree-dominator-opts" on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114902 --- Comment #18 from GCC Commits --- The releases/gcc-12 branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:840bc6741680a9c4b58fa1005f19a5d2e7d4be1f commit r12-10530-g840bc6741680a9c4b58fa1005f19a5d2e7d4be1f Author: Jakub Jelinek Date: Wed May 15 18:37:17 2024 +0200 combine: Fix up simplify_compare_const [PR115092] The following testcases are miscompiled (with tons of GIMPLE optimization disabled) because combine sees GE comparison of 1-bit sign_extract (i.e. something with [-1, 0] value range) with (const_int -1) (which is always true) and optimizes it into NE comparison of 1-bit zero_extract ([0, 1] value range) against (const_int 0). The reason is that simplify_compare_const first (correctly) simplifies the comparison to GE (ashift:SI something (const_int 31)) (const_int -2147483648) and then an optimization for when the second operand is power of 2 triggers. That optimization is fine for power of 2s which aren't the signed minimum of the mode, or if it is NE, EQ, GEU or LTU against the signed minimum of the mode, but for GE or LT optimizing it into NE (or EQ) against const0_rtx is wrong, those cases are always true or always false (but the function doesn't have a standardized way to tell callers the comparison is now unconditional). The following patch just disables the optimization in that case. 2024-05-15 Jakub Jelinek PR rtl-optimization/114902 PR rtl-optimization/115092 * combine.cc (simplify_compare_const): Don't optimize GE op0 SIGNED_MIN or LT op0 SIGNED_MIN into NE op0 const0_rtx or EQ op0 const0_rtx. * gcc.dg/pr114902.c: New test. * gcc.dg/pr115092.c: New test. (cherry picked from commit 0b93a0ae153ef70a82ff63e67926a01fdab9956b)
[Bug rtl-optimization/114902] [14 Regression] wrong code at -O3 with "-fno-tree-vrp -fno-expensive-optimizations -fno-tree-dominator-opts" on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114902 --- Comment #17 from GCC Commits --- The releases/gcc-13 branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:8deaab6f79768700e1bf05fe6af83b185f678b7f commit r13-8833-g8deaab6f79768700e1bf05fe6af83b185f678b7f Author: Jakub Jelinek Date: Wed May 15 18:37:17 2024 +0200 combine: Fix up simplify_compare_const [PR115092] The following testcases are miscompiled (with tons of GIMPLE optimization disabled) because combine sees GE comparison of 1-bit sign_extract (i.e. something with [-1, 0] value range) with (const_int -1) (which is always true) and optimizes it into NE comparison of 1-bit zero_extract ([0, 1] value range) against (const_int 0). The reason is that simplify_compare_const first (correctly) simplifies the comparison to GE (ashift:SI something (const_int 31)) (const_int -2147483648) and then an optimization for when the second operand is power of 2 triggers. That optimization is fine for power of 2s which aren't the signed minimum of the mode, or if it is NE, EQ, GEU or LTU against the signed minimum of the mode, but for GE or LT optimizing it into NE (or EQ) against const0_rtx is wrong, those cases are always true or always false (but the function doesn't have a standardized way to tell callers the comparison is now unconditional). The following patch just disables the optimization in that case. 2024-05-15 Jakub Jelinek PR rtl-optimization/114902 PR rtl-optimization/115092 * combine.cc (simplify_compare_const): Don't optimize GE op0 SIGNED_MIN or LT op0 SIGNED_MIN into NE op0 const0_rtx or EQ op0 const0_rtx. * gcc.dg/pr114902.c: New test. * gcc.dg/pr115092.c: New test. (cherry picked from commit 0b93a0ae153ef70a82ff63e67926a01fdab9956b)
[Bug rtl-optimization/114902] [14 Regression] wrong code at -O3 with "-fno-tree-vrp -fno-expensive-optimizations -fno-tree-dominator-opts" on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114902 Jakub Jelinek changed: What|Removed |Added Resolution|--- |FIXED Status|ASSIGNED|RESOLVED --- Comment #16 from Jakub Jelinek --- Fixed.
[Bug rtl-optimization/114902] [14 Regression] wrong code at -O3 with "-fno-tree-vrp -fno-expensive-optimizations -fno-tree-dominator-opts" on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114902 --- Comment #15 from GCC Commits --- The releases/gcc-14 branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:14a7296d04474055bfe1d7f130dceac6dabf390d commit r14-10276-g14a7296d04474055bfe1d7f130dceac6dabf390d Author: Jakub Jelinek Date: Wed May 15 18:37:17 2024 +0200 combine: Fix up simplify_compare_const [PR115092] The following testcases are miscompiled (with tons of GIMPLE optimization disabled) because combine sees GE comparison of 1-bit sign_extract (i.e. something with [-1, 0] value range) with (const_int -1) (which is always true) and optimizes it into NE comparison of 1-bit zero_extract ([0, 1] value range) against (const_int 0). The reason is that simplify_compare_const first (correctly) simplifies the comparison to GE (ashift:SI something (const_int 31)) (const_int -2147483648) and then an optimization for when the second operand is power of 2 triggers. That optimization is fine for power of 2s which aren't the signed minimum of the mode, or if it is NE, EQ, GEU or LTU against the signed minimum of the mode, but for GE or LT optimizing it into NE (or EQ) against const0_rtx is wrong, those cases are always true or always false (but the function doesn't have a standardized way to tell callers the comparison is now unconditional). The following patch just disables the optimization in that case. 2024-05-15 Jakub Jelinek PR rtl-optimization/114902 PR rtl-optimization/115092 * combine.cc (simplify_compare_const): Don't optimize GE op0 SIGNED_MIN or LT op0 SIGNED_MIN into NE op0 const0_rtx or EQ op0 const0_rtx. * gcc.dg/pr114902.c: New test. * gcc.dg/pr115092.c: New test. (cherry picked from commit 0b93a0ae153ef70a82ff63e67926a01fdab9956b)
[Bug rtl-optimization/114902] [14 Regression] wrong code at -O3 with "-fno-tree-vrp -fno-expensive-optimizations -fno-tree-dominator-opts" on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114902 Jakub Jelinek changed: What|Removed |Added Summary|[14/15 Regression] wrong|[14 Regression] wrong code |code at -O3 with|at -O3 with "-fno-tree-vrp |"-fno-tree-vrp |-fno-expensive-optimization |-fno-expensive-optimization |s -fno-tree-dominator-opts" |s -fno-tree-dominator-opts" |on x86_64-linux-gnu |on x86_64-linux-gnu | CC||jakub at gcc dot gnu.org Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org --- Comment #14 from Jakub Jelinek --- Fixed for 15.1+ so far.
