https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99293
Bug ID: 99293
Summary: Built-in vec_splat generates sub-optimal code for
-mcpu=power10
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: munroesj at gcc dot gnu.org
Target Milestone: ---
Created attachment 50263
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50263&action=edit
Simplified test case
While adding code to Power Vector Library (PVECLIB), for the POWER10 target, I
see strange code generation for Altivec built-in vec_splat for the vector long
long type. I would expect a xxpermdi (xxspltd) based on the "Power Vector
Intrinsic Programming Reference".
But I see the following generated:
0000000000000300 <test_vec_rlq_PWR10>:
300: 67 02 69 7c mfvsrld r9,vs35
304: 67 4b 09 7c mtvsrdd vs32,r9,r9
308: 05 00 42 10 vrlq v2,v2,v0
30c: 20 00 80 4e blr
While these seems to functionally correct, the trip through the GPR seems
unnecessary. It requires two serially dependent instructions where a single
xxspltd would do. I expected:
0000000000000300 <test_vec_rlq_PWR10>:
300: 57 1b 63 f0 xxspltd vs35,vs35,1
304: 05 18 42 10 vrlq v2,v2,v3
308: 20 00 80 4e blr
The compiler was:
Compiler: gcc version 10.2.1 20210104 (Advance-Toolchain 14.0-2) [2093e873bb6c]
(GCC)
