Missed instcombine transformation:
define i32 @a(i32 %x) nounwind readnone {
entry:
- %shr = lshr i32 %x, 5 ; <i32> [#uses=1]
- %xor = xor i32 %shr, 67108864 ; <i32> [#uses=1]
- %sub = add i32 %xor, -67108864 ; <i32> [#uses=1]
+ %rem = srem i32 %x, 32
+ %shl = shl i32 1, %rem
+ ret i32 %shl
+}
+
+The srem can be transformed to an and because if x is negative, the shift is
+undefined. Testcase derived from gcc.
+
+//===---------------------------------------------------------------------===//
+
+Missed instcombine/dagcombine transformation:
+define i32 @a(i32 %x, i32 %y) nounwind readnone {
+entry:
+ %mul = mul i32 %y, -8
+ %sub = sub i32 %x, %mul
ret i32 %sub
}
-This function is equivalent to "ashr i32 %x, 5". Testcase derived from gcc.
+Should compile to something like x+y*8, but currently compiles to an
+inefficient result. Testcase derived from gcc.
//===---------------------------------------------------------------------===//
-isSafeToLoadUnconditionally should allow a GEP of a global/alloca with constant
-indicies within the bounds of the allocated object. Reduced example:
+Missed instcombine/dagcombine transformation:
+define void @lshift_lt(i8 zeroext %a) nounwind {
+entry:
+ %conv = zext i8 %a to i32
+ %shl = shl i32 %conv, 3
+ %cmp = icmp ult i32 %shl, 33
+ br i1 %cmp, label %if.then, label %if.end
-const int a[] = {3,6};
-int b(int y) { int* x = y ? &a[0] : &a[1]; return *x; }
+if.then:
+ tail call void @bar() nounwind
+ ret void
-All the loads should be eliminated. Testcase derived from gcc.
+if.end:
+ ret void
+}
+declare void @bar() nounwind
+
+The shift should be eliminated. Testcase derived from gcc.
//===---------------------------------------------------------------------===//
+
+These compile into different code, one gets recognized as a switch and the
+other doesn't due to phase ordering issues (PR6212):
+
+int test1(int mainType, int subType) {
+ if (mainType == 7)
+ subType = 4;
+ else if (mainType == 9)
+ subType = 6;
+ else if (mainType == 11)
+ subType = 9;
+ return subType;
+}
+
+int test2(int mainType, int subType) {
+ if (mainType == 7)
+ subType = 4;
+ if (mainType == 9)
+ subType = 6;
+ if (mainType == 11)
+ subType = 9;
+ return subType;
+}
+
+//===---------------------------------------------------------------------===//
+
+The following test case (from PR6576):
+
+define i32 @mul(i32 %a, i32 %b) nounwind readnone {
+entry:
+ %cond1 = icmp eq i32 %b, 0 ; <i1> [#uses=1]
+ br i1 %cond1, label %exit, label %bb.nph
+bb.nph: ; preds = %entry
+ %tmp = mul i32 %b, %a ; <i32> [#uses=1]
+ ret i32 %tmp
+exit: ; preds = %entry
+ ret i32 0
+}
+
+could be reduced to:
+
+define i32 @mul(i32 %a, i32 %b) nounwind readnone {
+entry:
+ %tmp = mul i32 %b, %a
+ ret i32 %tmp
+}
+
+//===---------------------------------------------------------------------===//
+