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8 Commits

Author SHA1 Message Date
Chris Lattner 97bbee2fb4 Fix a miscompilation I introduced in r129652, thanks for Eli for tracking 
it down.  we effectively were compile the testcase into:

void test14(int x) {
  switch (x) {
    case 11: break;
    case 42: test14(97);  // fallthrough
    default: test14(42); break;

which is not the same thing at all.  This fixes a miscompilation of 
MallocBench/gs seen on the clang-x86_64-linux-fnt buildbot.

llvm-svn: 129679
 2011-04-17 23:21:26 +00:00
Chris Lattner 38b6057a93 when assertions are disabled, labels go away. Hopefully fixes the windows build. 
llvm-svn: 129660
 2011-04-17 16:19:57 +00:00
Chris Lattner bc204c8043 implement rdar://9289524 - case followed immediately by break results in empty IR block, 
a -O0 code quality issue.

llvm-svn: 129652
 2011-04-17 00:54:30 +00:00
Chris Lattner 35d3ac5e9e Make skipping of vardecls more precise: it's ok to skip a decl if the entire 
compound stmt containing the decl is skipped.

llvm-svn: 126639
 2011-02-28 07:22:44 +00:00
Chris Lattner 62208c395a make switch constant folding a bit stronger, handling a missed case. 
llvm-svn: 126638
 2011-02-28 07:16:14 +00:00
Chris Lattner dc2cc67e57 remove a bogus assertion, add a comment. 
llvm-svn: 126603
 2011-02-28 01:06:02 +00:00
Chris Lattner 0709542628 make switch condition constant folding much more aggressive, handling 
compound statements and break statements.  This implements enough to 
handle PR9322 and rdar://6970405.

llvm-svn: 126602
 2011-02-28 01:02:29 +00:00
Chris Lattner 0725a8b653 First tiny step to implementing PR9322: build infrastructure for only emitting the 
live case of a switch statement when switching on a constant.  This is terribly
limited, but enough to handle the trivial example included.  Before we would 
emit:

define void @test1(i32 %i) nounwind {
entry:
  %i.addr = alloca i32, align 4
  store i32 %i, i32* %i.addr, align 4
  switch i32 1, label %sw.epilog [
    i32 1, label %sw.bb
  ]

sw.bb:                                            ; preds = %entry
  %tmp = load i32* %i.addr, align 4
  %inc = add nsw i32 %tmp, 1
  store i32 %inc, i32* %i.addr, align 4
  br label %sw.epilog

sw.epilog:                                        ; preds = %sw.bb, %entry
  switch i32 0, label %sw.epilog3 [
    i32 1, label %sw.bb1
  ]

sw.bb1:                                           ; preds = %sw.epilog
  %tmp2 = load i32* %i.addr, align 4
  %add = add nsw i32 %tmp2, 2
  store i32 %add, i32* %i.addr, align 4
  br label %sw.epilog3

sw.epilog3:                                       ; preds = %sw.bb1, %sw.epilog
  ret void
}

now we emit:

define void @test1(i32 %i) nounwind {
entry:
  %i.addr = alloca i32, align 4
  store i32 %i, i32* %i.addr, align 4
  %tmp = load i32* %i.addr, align 4
  %inc = add nsw i32 %tmp, 1
  store i32 %inc, i32* %i.addr, align 4
  ret void
}

This improves -O0 compile time (less IR to generate and shove through the code 
generator) and the clever linux kernel people found a way to fail to build if we 
don't do this optimization.  This step isn't enough to handle the kernel case
though.

llvm-svn: 126597
 2011-02-28 00:22:07 +00:00