[GHC] #14830: Use test instead of cmp for comparison against zero.
#14830: Use test instead of cmp for comparison against zero. -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: task | Status: new Priority: low | Milestone: Component: Compiler | Version: (NCG) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- For comparisons `test r, r` and `cmp r, $0` are interchangeable at least on x86. However using test leads to slightly smaller code. (Saves a byte per comparison). A good starting point is stmtToInstrs in compiler/nativeGen/X86/CodeGen starting with how CmmCondBranch is compiled to Instructions. From there it should be not too hard to track down the required changes. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14830 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14830: Use test instead of cmp for comparison against zero. -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: task | Status: new Priority: low | Milestone: Component: Compiler (NCG) | Version: Resolution: | Keywords: CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by AndreasK): * keywords: => CodeGen -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14830#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14830: Use test instead of cmp for comparison against zero. -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: task | Status: new Priority: low | Milestone: Component: Compiler (NCG) | Version: Resolution: | Keywords: CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by vanessamchale): `stmtToInstrs` calls `genCondJump` which as far as I can tell only uses `cmp` on registers, not immediate values. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14830#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14830: Use test instead of cmp for comparison against zero. -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: task | Status: new Priority: low | Milestone: Component: Compiler (NCG) | Version: Resolution: | Keywords: CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by vanessamchale): * cc: vanessa.mchale@… (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14830#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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