Compile following code with options -march=armv7-a -mthumb -Os int foo(); long long bar22() { int result = foo(); return result; } GCC generates: bar22: push {r3, lr} bl foo asrs r3, r0, #31 // A mov r1, r3 // B pop {r3, pc} Instruction A,B can be simplified to "asrs r1, r0, #31". In rtl expand, result was first extended to a DI register and then the DI register was moved to return register. In later passs the low half of the return value and variable result were recognized as in the same register, so the low part move was removed. After register allocation I get: (call_insn 5 2 7 2 src/t5.c:5 (parallel [ (set (reg:SI 0 r0) (call (mem:SI (symbol_ref:SI ("foo") [flags 0x41] <function_decl 0x7f6e60fe0600 foo>) [0 S4 A32]) (const_int 0 [0x0]))) (use (const_int 0 [0x0])) (clobber (reg:SI 14 lr)) ]) 255 {*call_value_insn} (nil) (nil)) (insn 7 5 22 2 src/t5.c:5 (set (reg:DI 2 r2 [orig:136 result ] [136]) (sign_extend:DI (reg/v:SI 0 r0 [orig:133 result ] [133]))) 691 {*thumb2_extendsidi2} (nil)) (insn 22 7 15 2 src/t5.c:7 (set (reg:SI 1 r1 [+4 ]) (reg:SI 3 r3 [ result+4 ])) 658 {*thumb2_movsi_insn} (nil)) The high part register move didn't get any chance to be removed until the end of compilation.
Confirmed.
Subject: Bug 43137 Author: bernds Date: Mon Sep 6 22:32:26 2010 New Revision: 163935 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=163935 Log: PR target/43137 * config/arm/iterators.md (qhs_zextenddi_cond, qhs_sextenddi_cond): New define_mode_attrs. * config/arm/arm.md (zero_extendsidi2, arm_zero_extendsidi2, arm_exxtendsidi2, arm_extendsidi2): Delete patterns. (zero_extend<mode>di2, extend<mode>di2 and related splits): New. (thumb1_zero_extendhisi2): Remove code to handle LABEL_REFs. Remove pool_range attribute. (arm_zero_extendhisi2, arm_zero_extendhisi2_v6, arm_zero_extendqisi2, arm_zero_extendqisi2_v6, thumb1_zero_extendqisi2_v6): Remove pool_range and neg_pool_range attributes. * config/arm/thumb2.md (thumb2_zero_extendsidi2, thumb2_zero_extendhidi2, thumb2_zero_extendqidi2, thumb2_extendsidi2, thumb2_extendhidi2, thumb2_extendqidi2): Delete. PR target/43137 * gcc.target/arm/pr43137.c: New test. Added: trunk/gcc/testsuite/gcc.target/arm/pr43137.c Modified: trunk/gcc/ChangeLog trunk/gcc/config/arm/arm.md trunk/gcc/config/arm/iterators.md trunk/gcc/config/arm/thumb2.md trunk/gcc/testsuite/ChangeLog
Fixed.