diff options
Diffstat (limited to 'compiler/codeGen')
| -rw-r--r-- | compiler/codeGen/StgCmmExpr.hs | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/compiler/codeGen/StgCmmExpr.hs b/compiler/codeGen/StgCmmExpr.hs index c2f2efed3d..22fcfaf412 100644 --- a/compiler/codeGen/StgCmmExpr.hs +++ b/compiler/codeGen/StgCmmExpr.hs @@ -60,7 +60,8 @@ cgExpr :: StgExpr -> FCode ReturnKind cgExpr (StgApp fun args) = cgIdApp fun args -{- seq# a s ==> a -} +-- seq# a s ==> a +-- See Note [seq# magic] in PrelRules cgExpr (StgOpApp (StgPrimOp SeqOp) [StgVarArg a, _] _res_ty) = cgIdApp a [] @@ -447,13 +448,14 @@ cgCase scrut@(StgApp v []) _ (PrimAlt _) _ {- Note [Handle seq#] ~~~~~~~~~~~~~~~~~~~~~ -case seq# a s of v - (# s', a' #) -> e +See Note [seq# magic] in PrelRules. +The special case for seq# in cgCase does this: + case seq# a s of v + (# s', a' #) -> e ==> - -case a of v - (# s', a' #) -> e + case a of v + (# s', a' #) -> e (taking advantage of the fact that the return convention for (# State#, a #) is the same as the return convention for just 'a') @@ -461,6 +463,7 @@ is the same as the return convention for just 'a') cgCase (StgOpApp (StgPrimOp SeqOp) [StgVarArg a, _] _) bndr alt_type alts = -- Note [Handle seq#] + -- And see Note [seq# magic] in PrelRules -- Use the same return convention as vanilla 'a'. cgCase (StgApp a []) bndr alt_type alts |