maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Teach InstCombine to merge (icmp ult (X + CA), C1) | (icmp eq X, C2) into (icmp ult (X + CA), C1 + 1) if C2 + CA == C1. 

InstCombine creates these so now we compile x == 23 || x == 24 || x == 25 to
  %x.off = add i32 %x, -23
  %1 = icmp ult i32 %x.off, 3
instead of
  %x.off = add i32 %x, -23
  %1 = icmp ult i32 %x.off, 2
  %cmp3 = icmp eq i32 %x, 25
  %ret2 = or i1 %1, %cmp3

llvm-svn: 122248
This commit is contained in:
Benjamin Kramer 2010-12-20 16:18:51 +00:00
parent ca2511d849
commit 68531baea9
2 changed files with 24 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1450,7 +1450,16 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
return Builder->CreateICmp(LHSCC, NewOr, LHSCst);
}
}
// (icmp ult (X + CA), C1) | (icmp eq X, C2) -> (icmp ult (X + CA), C1 + 1)
// iff C2 + CA == C1.
if (LHSCC == ICmpInst::ICMP_ULT) {
ConstantInt *AddCst;
if (match(Val, m_Add(m_Specific(Val2), m_ConstantInt(AddCst))))
if (RHSCst->getValue() + AddCst->getValue() == LHSCst->getValue())
return Builder->CreateICmp(LHSCC, Val, AddOne(LHSCst));
}
// From here on, we only handle:
// (icmp1 A, C1) | (icmp2 A, C2) --> something simpler.
if (Val != Val2) return 0;

14
llvm/test/Transforms/InstCombine/or.ll
View File

@ -376,3 +376,17 @@ define i32 @test35(i32 %a, i32 %b) {
; CHECK-NEXT: or i32 %a, %b
; CHECK-NEXT: or i32 %1, 1135
}
define i1 @test36(i32 %x) {
%cmp1 = icmp eq i32 %x, 23
%cmp2 = icmp eq i32 %x, 24
%ret1 = or i1 %cmp1, %cmp2
%cmp3 = icmp eq i32 %x, 25
%ret2 = or i1 %ret1, %cmp3
ret i1 %ret2
; CHECK: @test36
; CHECK-NEXT: %x.off = add i32 %x, -23
; CHECK-NEXT: icmp ult i32 %x.off, 3
; CHECK-NEXT: ret i1
}