diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 6f1ab31fe03b..a53f825f43a8 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2814,8 +2814,15 @@ Instruction *InstCombinerImpl::foldICmpDivConstant(ICmpInst &Cmp,
   // (x /u C2) <u C.  Simply casting the operands and result won't
   // work. :(  The if statement below tests that condition and bails
   // if it finds it.
-  if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
-    return nullptr;
+  // However, when the divisor is a positive constant and the dividend is
+  // known non-negative, sdiv is equivalent to udiv, so we can lower
+  // DivIsSigned and proceed through the unsigned path.
+  if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned()) {
+    if (!DivIsSigned || !C2->isStrictlyPositive() ||
+        !isKnownNonNegative(X, SQ.getWithInstruction(&Cmp)))
+      return nullptr;
+    DivIsSigned = false;
+  }
 
   // The ProdOV computation fails on divide by 0 and divide by -1. Cases with
   // INT_MIN will also fail if the divisor is 1. Although folds of all these
diff --git a/llvm/test/Transforms/InstCombine/icmp-sdiv-assume.ll b/llvm/test/Transforms/InstCombine/icmp-sdiv-assume.ll
new file mode 100644
index 000000000000..27c0ff485c5e
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/icmp-sdiv-assume.ll
@@ -0,0 +1,209 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+; Test that foldICmpDivConstant can treat sdiv as udiv when the dividend
+; is known non-negative (e.g. via a dominating condition), allowing the
+; fold to proceed despite a signed div / unsigned icmp mismatch.
+; Non-power-of-two divisors are used to prevent sdiv->lshr conversion.
+; The sdiv is placed in the entry block where x's sign is unknown, and
+; the icmp is in a block dominated by a condition that proves x >= 0.
+
+declare void @use(i32)
+
+; Positive test: x > 255 dominates the icmp, proving x non-negative.
+; sdiv(x, 65) = udiv(x, 65) when x >= 0, and udiv(x, 65) > 2 when x >= 195.
+; Since x > 255 >= 195, the result folds to true.
+define i1 @icmp_sdiv_domcond(i32 %x) {
+; CHECK-LABEL: @icmp_sdiv_domcond(
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[X:%.*]], 65
+; CHECK-NEXT:    call void @use(i32 [[DIV]])
+; CHECK-NEXT:    [[COND:%.*]] = icmp sgt i32 [[X]], 255
+; CHECK-NEXT:    br i1 [[COND]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
+; CHECK:       if.true:
+; CHECK-NEXT:    ret i1 true
+; CHECK:       if.false:
+; CHECK-NEXT:    ret i1 false
+;
+  %div = sdiv i32 %x, 65
+  call void @use(i32 %div)
+  %cond = icmp sgt i32 %x, 255
+  br i1 %cond, label %if.true, label %if.false
+
+if.true:
+  %cmp = icmp samesign ugt i32 %div, 2
+  ret i1 %cmp
+
+if.false:
+  ret i1 false
+}
+
+; Positive test: add+sdiv pattern (mirrors real-world kernel case).
+; x+63 > 255 dominates the icmp, proving x+63 non-negative.
+define i1 @icmp_add_sdiv_domcond(i32 %x) {
+; CHECK-LABEL: @icmp_add_sdiv_domcond(
+; CHECK-NEXT:    [[ADD:%.*]] = add i32 [[X:%.*]], 63
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[ADD]], 65
+; CHECK-NEXT:    call void @use(i32 [[DIV]])
+; CHECK-NEXT:    [[COND:%.*]] = icmp sgt i32 [[ADD]], 255
+; CHECK-NEXT:    br i1 [[COND]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
+; CHECK:       if.true:
+; CHECK-NEXT:    ret i1 true
+; CHECK:       if.false:
+; CHECK-NEXT:    ret i1 false
+;
+  %add = add i32 %x, 63
+  %div = sdiv i32 %add, 65
+  call void @use(i32 %div)
+  %cond = icmp sgt i32 %add, 255
+  br i1 %cond, label %if.true, label %if.false
+
+if.true:
+  %cmp = icmp samesign ugt i32 %div, 2
+  ret i1 %cmp
+
+if.false:
+  ret i1 false
+}
+
+; Positive test: udiv case (no signedness mismatch, baseline behavior).
+define i1 @icmp_udiv_domcond(i32 %x) {
+; CHECK-LABEL: @icmp_udiv_domcond(
+; CHECK-NEXT:    [[DIV:%.*]] = udiv i32 [[X:%.*]], 65
+; CHECK-NEXT:    call void @use(i32 [[DIV]])
+; CHECK-NEXT:    [[COND:%.*]] = icmp ugt i32 [[X]], 255
+; CHECK-NEXT:    br i1 [[COND]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
+; CHECK:       if.true:
+; CHECK-NEXT:    ret i1 true
+; CHECK:       if.false:
+; CHECK-NEXT:    ret i1 false
+;
+  %div = udiv i32 %x, 65
+  call void @use(i32 %div)
+  %cond = icmp ugt i32 %x, 255
+  br i1 %cond, label %if.true, label %if.false
+
+if.true:
+  %cmp = icmp ugt i32 %div, 2
+  ret i1 %cmp
+
+if.false:
+  ret i1 false
+}
+
+; Negative test: dominating condition is too weak.
+; x > 127 does NOT prove sdiv(x, 65) > 2 (e.g. x=128, sdiv(128,65)=1).
+define i1 @icmp_sdiv_domcond_too_weak(i32 %x) {
+; CHECK-LABEL: @icmp_sdiv_domcond_too_weak(
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[X:%.*]], 65
+; CHECK-NEXT:    call void @use(i32 [[DIV]])
+; CHECK-NEXT:    [[COND:%.*]] = icmp sgt i32 [[X]], 127
+; CHECK-NEXT:    br i1 [[COND]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
+; CHECK:       if.true:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i32 [[X]], 194
+; CHECK-NEXT:    ret i1 [[CMP]]
+; CHECK:       if.false:
+; CHECK-NEXT:    ret i1 false
+;
+  %div = sdiv i32 %x, 65
+  call void @use(i32 %div)
+  %cond = icmp sgt i32 %x, 127
+  br i1 %cond, label %if.true, label %if.false
+
+if.true:
+  %cmp = icmp samesign ugt i32 %div, 2
+  ret i1 %cmp
+
+if.false:
+  ret i1 false
+}
+
+; Negative test: no dominating condition, x's sign is unknown.
+define i1 @icmp_sdiv_no_domcond(i32 %x) {
+; CHECK-LABEL: @icmp_sdiv_no_domcond(
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[X:%.*]], 65
+; CHECK-NEXT:    [[CMP:%.*]] = icmp samesign ugt i32 [[DIV]], 2
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %div = sdiv i32 %x, 65
+  %cmp = icmp samesign ugt i32 %div, 2
+  ret i1 %cmp
+}
+
+; Negative test: comparison is on the boundary.
+; x > 194 means x >= 195, sdiv(195, 65) = 3, but 3 > 3 is false.
+define i1 @icmp_sdiv_domcond_boundary(i32 %x) {
+; CHECK-LABEL: @icmp_sdiv_domcond_boundary(
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[X:%.*]], 65
+; CHECK-NEXT:    call void @use(i32 [[DIV]])
+; CHECK-NEXT:    [[COND:%.*]] = icmp sgt i32 [[X]], 194
+; CHECK-NEXT:    br i1 [[COND]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
+; CHECK:       if.true:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i32 [[X]], 259
+; CHECK-NEXT:    ret i1 [[CMP]]
+; CHECK:       if.false:
+; CHECK-NEXT:    ret i1 false
+;
+  %div = sdiv i32 %x, 65
+  call void @use(i32 %div)
+  %cond = icmp sgt i32 %x, 194
+  br i1 %cond, label %if.true, label %if.false
+
+if.true:
+  %cmp = icmp samesign ugt i32 %div, 3
+  ret i1 %cmp
+
+if.false:
+  ret i1 false
+}
+
+; Negative test: dividend is known negative, sdiv != udiv.
+define i1 @icmp_sdiv_negative_dividend(i32 %x) {
+; CHECK-LABEL: @icmp_sdiv_negative_dividend(
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[X:%.*]], 65
+; CHECK-NEXT:    call void @use(i32 [[DIV]])
+; CHECK-NEXT:    [[COND:%.*]] = icmp slt i32 [[X]], -100
+; CHECK-NEXT:    br i1 [[COND]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
+; CHECK:       if.true:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp samesign ugt i32 [[DIV]], 2
+; CHECK-NEXT:    ret i1 [[CMP]]
+; CHECK:       if.false:
+; CHECK-NEXT:    ret i1 false
+;
+  %div = sdiv i32 %x, 65
+  call void @use(i32 %div)
+  %cond = icmp slt i32 %x, -100
+  br i1 %cond, label %if.true, label %if.false
+
+if.true:
+  %cmp = icmp samesign ugt i32 %div, 2
+  ret i1 %cmp
+
+if.false:
+  ret i1 false
+}
+
+; Negative test: divisor is negative, sdiv(x, -65) != udiv(x, -65).
+define i1 @icmp_sdiv_negative_divisor(i32 %x) {
+; CHECK-LABEL: @icmp_sdiv_negative_divisor(
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[X:%.*]], -65
+; CHECK-NEXT:    call void @use(i32 [[DIV]])
+; CHECK-NEXT:    [[COND:%.*]] = icmp sgt i32 [[X]], 255
+; CHECK-NEXT:    br i1 [[COND]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
+; CHECK:       if.true:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp samesign ugt i32 [[DIV]], 2
+; CHECK-NEXT:    ret i1 [[CMP]]
+; CHECK:       if.false:
+; CHECK-NEXT:    ret i1 false
+;
+  %div = sdiv i32 %x, -65
+  call void @use(i32 %div)
+  %cond = icmp sgt i32 %x, 255
+  br i1 %cond, label %if.true, label %if.false
+
+if.true:
+  %cmp = icmp samesign ugt i32 %div, 2
+  ret i1 %cmp
+
+if.false:
+  ret i1 false
+}