+(or better) not:
+
+__Z11no_overflowjj:
+ add r2, r4, r3
+ cmplw cr7, r2, r3
+ mfcr r2
+ rlwinm r2, r2, 29, 31, 31
+ xori r3, r2, 1
+ blr
+
+//===---------------------------------------------------------------------===//
+
+We compile some FP comparisons into an mfcr with two rlwinms and an or. For
+example:
+#include <math.h>
+int test(double x, double y) { return islessequal(x, y);}
+int test2(double x, double y) { return islessgreater(x, y);}
+int test3(double x, double y) { return !islessequal(x, y);}
+
+Compiles into (all three are similar, but the bits differ):
+
+_test:
+ fcmpu cr7, f1, f2
+ mfcr r2
+ rlwinm r3, r2, 29, 31, 31
+ rlwinm r2, r2, 31, 31, 31
+ or r3, r2, r3
+ blr
+
+GCC compiles this into:
+
+ _test:
+ fcmpu cr7,f1,f2
+ cror 30,28,30
+ mfcr r3
+ rlwinm r3,r3,31,1
+ blr
+
+which is more efficient and can use mfocr. See PR642 for some more context.
+
+//===---------------------------------------------------------------------===//
+
+void foo(float *data, float d) {
+ long i;
+ for (i = 0; i < 8000; i++)
+ data[i] = d;
+}
+void foo2(float *data, float d) {
+ long i;
+ data--;
+ for (i = 0; i < 8000; i++) {
+ data[1] = d;
+ data++;
+ }
+}
+
+These compile to:
+
+_foo:
+ li r2, 0
+LBB1_1: ; bb
+ addi r4, r2, 4
+ stfsx f1, r3, r2
+ cmplwi cr0, r4, 32000
+ mr r2, r4
+ bne cr0, LBB1_1 ; bb
+ blr
+_foo2:
+ li r2, 0
+LBB2_1: ; bb
+ addi r4, r2, 4
+ stfsx f1, r3, r2
+ cmplwi cr0, r4, 32000
+ mr r2, r4
+ bne cr0, LBB2_1 ; bb
+ blr
+
+The 'mr' could be eliminated to folding the add into the cmp better.
+
+//===---------------------------------------------------------------------===//
+Codegen for the following (low-probability) case deteriorated considerably
+when the correctness fixes for unordered comparisons went in (PR 642, 58871).
+It should be possible to recover the code quality described in the comments.
+
+; RUN: llvm-as < %s | llc -march=ppc32 | grep or | count 3
+; This should produce one 'or' or 'cror' instruction per function.
+
+; RUN: llvm-as < %s | llc -march=ppc32 | grep mfcr | count 3
+; PR2964
+
+define i32 @test(double %x, double %y) nounwind {
+entry:
+ %tmp3 = fcmp ole double %x, %y ; <i1> [#uses=1]
+ %tmp345 = zext i1 %tmp3 to i32 ; <i32> [#uses=1]
+ ret i32 %tmp345
+}
+
+define i32 @test2(double %x, double %y) nounwind {
+entry:
+ %tmp3 = fcmp one double %x, %y ; <i1> [#uses=1]
+ %tmp345 = zext i1 %tmp3 to i32 ; <i32> [#uses=1]
+ ret i32 %tmp345
+}
+
+define i32 @test3(double %x, double %y) nounwind {
+entry:
+ %tmp3 = fcmp ugt double %x, %y ; <i1> [#uses=1]
+ %tmp34 = zext i1 %tmp3 to i32 ; <i32> [#uses=1]
+ ret i32 %tmp34
+}
+//===----------------------------------------------------------------------===//
+; RUN: llvm-as < %s | llc -march=ppc32 | not grep fneg
+
+; This could generate FSEL with appropriate flags (FSEL is not IEEE-safe, and
+; should not be generated except with -enable-finite-only-fp-math or the like).
+; With the correctness fixes for PR642 (58871) LowerSELECT_CC would need to
+; recognize a more elaborate tree than a simple SETxx.
+
+define double @test_FNEG_sel(double %A, double %B, double %C) {
+ %D = fsub double -0.000000e+00, %A ; <double> [#uses=1]
+ %Cond = fcmp ugt double %D, -0.000000e+00 ; <i1> [#uses=1]
+ %E = select i1 %Cond, double %B, double %C ; <double> [#uses=1]
+ ret double %E
+}
+
+//===----------------------------------------------------------------------===//
+The save/restore sequence for CR in prolog/epilog is terrible:
+- Each CR subreg is saved individually, rather than doing one save as a unit.
+- On Darwin, the save is done after the decrement of SP, which means the offset
+from SP of the save slot can be too big for a store instruction, which means we
+need an additional register (currently hacked in 96015+96020; the solution there
+is correct, but poor).
+- On SVR4 the same thing can happen, and I don't think saving before the SP
+decrement is safe on that target, as there is no red zone. This is currently
+broken AFAIK, although it's not a target I can exercise.
+The following demonstrates the problem:
+extern void bar(char *p);
+void foo() {
+ char x[100000];
+ bar(x);
+ __asm__("" ::: "cr2");
+}
+
+//===----------------------------------------------------------------------===//
+
+Instruction fusion was introduced in ISA 2.06 and more opportunities added in
+ISA 2.07. LLVM needs to add infrastructure to recognize fusion opportunities
+and force instruction pairs to be scheduled together.
+