Limit CSE of integer constants

Never do CSE for constants that fit in 32 bits signed. Do it only for constants that do not fit, and only on some 64-bit targets where the code generated for Iconst_int can be costly (ARM64, POWER, RISC-V).
ocaml · Sep 6, 2021 · 29d3fc7 · 29d3fc7
1 parent cd105d9
commit 29d3fc7
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Showing 4 changed files with 3 additions and 8 deletions.
diff --git a/asmcomp/arm/CSE.ml b/asmcomp/arm/CSE.ml
@@ -29,11 +29,6 @@ method! class_of_operation op =
   | Ispecific _ -> Op_pure
   | _ -> super#class_of_operation op
 
-method! is_cheap_operation op =
-  match op with
-  | Iconst_int n -> n <= 255n && n >= 0n
-  | _ -> false
-
 end
 
 let fundecl f =

diff --git a/asmcomp/arm64/CSE.ml b/asmcomp/arm64/CSE.ml
@@ -31,7 +31,7 @@ method! class_of_operation op =
 
 method! is_cheap_operation op =
   match op with
-  | Iconst_int n -> n <= 65535n && n >= 0n
+  | Iconst_int n -> n <= 0x7FFF_FFFFn && n >= -0x8000_0000n
   | _ -> false
 
 end

diff --git a/asmcomp/power/CSE.ml b/asmcomp/power/CSE.ml
@@ -31,7 +31,7 @@ method! class_of_operation op =
 
 method! is_cheap_operation op =
   match op with
-  | Iconst_int n -> n <= 32767n && n >= -32768n
+  | Iconst_int n -> n <= 0x7FFF_FFFFn && n >= -0x8000_0000n
   | _ -> false
 
 end

diff --git a/asmcomp/riscv/CSE.ml b/asmcomp/riscv/CSE.ml
@@ -30,7 +30,7 @@ method! class_of_operation op =
 
 method! is_cheap_operation op =
   match op with
-  | Iconst_int n -> n <= 0x7FFn && n >= -0x800n
+  | Iconst_int n -> n <= 0x7FFF_FFFFn && n >= -0x8000_0000n
   | _ -> false
 
 end