From 410e4850f38f275db6e3556d18885bfe4c259121 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Fri, 8 Nov 2002 15:21:28 +0000
Subject: [PATCH] [project @ 2002-11-08 15:21:27 by simonpj]
 -------------------------------- 	Expression
 simplification for TH 	--------------------------------

Simplify expressions without any inlining in SimplCore.simplifyExpr.

simplifyExpr is used to simplify a TH splice before running the code,
and simplifyExpr was using (SimplPhase 0) which allows inlining.
Unfortunately, when -O is on (which can happen when compiling a program
with some splices with -O) some inlining can happen which then confuses
the byte-code generator.  (Unboxed tuples.)
---
 ghc/compiler/simplCore/SimplCore.lhs  |    7 ++++++-
 ghc/compiler/simplCore/SimplMonad.lhs |    8 ++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/ghc/compiler/simplCore/SimplCore.lhs b/ghc/compiler/simplCore/SimplCore.lhs
index 9acfd81..ad30c81 100644
--- a/ghc/compiler/simplCore/SimplCore.lhs
+++ b/ghc/compiler/simplCore/SimplCore.lhs
@@ -118,7 +118,7 @@ simplifyExpr dflags expr
 
 	; us <-  mkSplitUniqSupply 's'
 
-	; let env	       = emptySimplEnv (SimplPhase 0) [] emptyVarSet
+	; let env	       = emptySimplEnv SimplGently [] emptyVarSet
 	      (expr', _counts) = initSmpl dflags us (simplExprGently env expr)
 
 	; dumpIfSet_dyn dflags Opt_D_dump_simpl "Simplified expression"
@@ -362,6 +362,11 @@ simplExprGently :: SimplEnv -> CoreExpr -> SimplM CoreExpr
 --	alone leaves tons of crud.
 -- Used (a) for user expressions typed in at the interactive prompt
 --	(b) the LHS and RHS of a RULE
+--
+-- The name 'Gently' suggests that the SimplifierMode is SimplGently,
+-- and in fact that is so.... but the 'Gently' in simplExprGently doesn't
+-- enforce that; it just simplifies the expression twice
+
 simplExprGently env expr
   = simplExpr env (occurAnalyseGlobalExpr expr) 	`thenSmpl` \ expr1 ->
     simplExpr env (occurAnalyseGlobalExpr expr1)
diff --git a/ghc/compiler/simplCore/SimplMonad.lhs b/ghc/compiler/simplCore/SimplMonad.lhs
index fe43c6d..5edfd2c 100644
--- a/ghc/compiler/simplCore/SimplMonad.lhs
+++ b/ghc/compiler/simplCore/SimplMonad.lhs
@@ -682,6 +682,8 @@ settings:
 	SimplGently	(a) Simplifying before specialiser/full laziness
 			(b) Simplifiying inside INLINE pragma
 			(c) Simplifying the LHS of a rule
+			(d) Simplifying a GHCi expression or Template 
+				Haskell splice
 
 	SimplPhase n	Used at all other times
 
@@ -693,6 +695,12 @@ because doing so inhibits floating
     ==> ...(case x of I# x# -> case fw x# of ...)...
 and now the redex (f x) isn't floatable any more.
 
+The no-inling thing is also important for Template Haskell.  You might be 
+compiling in one-shot mode with -O2; but when TH compiles a splice before
+running it, we don't want to use -O2.  Indeed, we don't want to inline
+anything, because the byte-code interpreter might get confused about 
+unboxed tuples and suchlike.
+
 INLINE pragmas
 ~~~~~~~~~~~~~~
 SimplGently is also used as the mode to simplify inside an InlineMe note.
-- 
1.7.10.4