192073 2018-11-28 00:21:34 -0800 [JSC] FTL should not load arguments twice for type check and use for non-full-64bit values 2023-06-02 18:42:29 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 saam ysuzuki benjamin fpizlo ggaren gskachkov keith_miller mark.lam msaboff rmorisset ticaiolima webkit-bug-importer ysuzuki oldest_to_newest 1482377 0 saam 2018-11-28 00:21:34 -0800 We end up loading the arguments twice just to have the second loads be 32-bit loads. We shouldn't have to do this. a & b are ints: ``` function foo(a, b) { return a + b; } ``` Generates: ``` 0x4c04f0c024ed: mov 0x38(%rbp), %rcx 0x4c04f0c024f1: mov $0xffff000000000000, %rax 0x4c04f0c024fb: cmp %rax, %rcx 0x4c04f0c024fe: jb 0x4c04f0c02595 0x4c04f0c02504: mov 0x30(%rbp), %rcx 0x4c04f0c02508: cmp %rax, %rcx 0x4c04f0c0250b: jb 0x4c04f0c0259f 0x4c04f0c02511: mov 0x30(%rbp), %ecx 0x4c04f0c02514: mov 0x38(%rbp), %edx 0x4c04f0c02517: add %ecx, %edx 0x4c04f0c02519: jo 0x4c04f0c025b3 0x4c04f0c0251f: add %rdx, %rax 0x4c04f0c02526: ret ``` 1482426 1 fpizlo 2018-11-28 07:26:40 -0800 And the FTL is emitting the loads twice? This could be restated as an FTL lowering bug. But I agree that CSE should be smart enough to manufacture a Trunc on the originally loaded value. 1496362 2 saam 2019-01-20 13:05:54 -0800 (In reply to Filip Pizlo from comment #1) > And the FTL is emitting the loads twice? Yeah it could, but it'd be awkward to do this in the FTL since the first loads are for proving argument types. I think it'd be nicer if B3 were just smart enough to do this.\ > > This could be restated as an FTL lowering bug. But I agree that CSE should > be smart enough to manufacture a Trunc on the originally loaded value. 1959368 3 webkit-bug-importer 2023-06-01 10:26:21 -0700 <rdar://problem/110121633> 1959369 4 ysuzuki 2023-06-01 10:29:05 -0700 Pull request: https://github.com/WebKit/WebKit/pull/14592 1959648 5 ews-feeder 2023-06-02 18:42:26 -0700 Committed 264846@main (4b922ed02257): <https://commits.webkit.org/264846@main> Reviewed commits have been landed. Closing PR #14592 and removing active labels.